Semiconductor display device

ABSTRACT

To provide a semiconductor display device capable of displaying an image having clarity and a desired color, even when the speed of deterioration of an EL layer is influenced by its environment. Display pixels and sensor pixels of an EL display each have an EL element, and the sensor pixels each have a diode. The luminance of the EL elements of each in the display pixels is controlled in accordance with the amount of electric current flowing in each of the diodes.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an EL display that is formed byfabricating an EL (Electro Luminescence) element on a substrate.Particularly, the present invention relates to an active matrix type ELdisplay that uses a semiconductor element (an element employing asemiconductor thin film), and furthermore to a semiconductor displaydevice employing the EL display.

2. Description of the Related Art

In recent years, technology for forming a TFT on a substrate has beenlargely improved, and an application development of the TFT to an activematrix type semiconductor display device has been carried out. Inparticular, the TFT using a polysilicon film has a higher electric fieldeffect mobility than the TFT using a conventional amorphous siliconfilm, and therefore, the TFT may be operated at a high speed. Thus, thepixel control which has been conducted at a driver circuit outside ofthe substrate may be conducted at the driver circuit which is formed onthe same substrate as the pixel.

Such an active matrix type semiconductor display device can, bypreparing various circuits and elements on the same substrate, obtainvarious advantages such as a decrease in manufacturing cost, a decreasein the size of the semiconductor display device, an increase in yield,and a decrease in throughput.

Further, research on the active matrix type EL display having an ELelement as a self-light-emitting element is becoming more and moreactive. The EL display is referred to as a light-emitting display, anorganic EL display (OELD) or an organic light-emitting diode (OLED).

The EL display is a self-light-emitting type unlike a liquid crystaldisplay device. The EL element is constituted such that a layercontaining an organic compound (hereinafter, referred to as an EL layer)is sandwiched between a pair of electrodes (anode and cathode). However,the EL layer normally has a lamination structure. Typically, thelamination structure of a “hole transport layer/a light emittinglayer/an electron transport layer” proposed by Tang et al. of theEastman Kodak Company can be cited. This structure has a very highlight-emitting efficiency, and this structure is adopted in almost allthe EL displays which are currently subjected to research anddevelopment.

When the EL element obtains Luminescence (Electro Luminescence) which isgenerated by applying a voltage to the EL element, it is composed of ananode layer an EL layer, and a cathode layer. There are two types ofluminescence in an organic compound, one being a luminescence that isgenerated when the organic compound returns from a singlet excitationstate to a around state (fluorescence) and the other being aluminescence that is generated when the organic compound returns from atriplet excitation state to a ground state (phosphorescence). Eithertype of luminescence may be used in the EL display of the presentinvention.

In addition, the structure may be such that on the electrodes, a holeinjection layer/a hole transport layer/a light emitting layer/anelectron transport layer, or a hole injection layer/a hole transportlayer/a light emitting layer/an electron transport layer/an electroninjection layer may be laminated in order. Phosphorescent dye or thelike may be doped into the light emitting layer.

In this specification, all the layers provided between a pair ofelectrodes are generally referred to as EL layers. Consequently, thehole injection layer, the hole transport layer, the light emittinglayer, the electron transport layer, the electron injection layer andthe like are all included in the EL layers.

In this specification, a light emitting element, which is composed of ananode, an EL layer and a cathode, is referred to as an EL element.

The deterioration of the EL material of the EL layer has become aproblem in the realization of the EL display, which leads to thereduction in the luminance of the EL element.

The EL material of the EL layer is inferior to moisture, oxygen, light,and heat, which are the factors that promote the deterioration of the ELlayer. To be more specific, the rate at which the EL layer deterioratesis influenced by the structure of a device driving the EL display,characteristics of the EL material structuring the EL layer, materialsof an electrode, conditions of the manufacturing processes, a drivingmethod of the EL display and the like.

The EL layer deteriorates even if a constant voltage from a pair ofelectrodes is applied thereto, whereby the luminance of the EL elementis reduced. Thus, an image displayed on the EL display is not clearbecause of the reduction in the luminance of the EL element.

Further, Color display systems of the EL display are roughly dividedinto four; a system where three kinds of EL elements corresponding to R(red), G (green), and B (blue), respectively, are formed; a system hereEL elements emitting white light are combined with a color filter; asystem where EL elements emitting blue or blue-green light are combinedwith a fluophor (fluorescent color conversion layer: CCM); and a systemwhere EL elements corresponding to R, G, and B are superimposed on atransparent electrode used as a cathode (an opposing electrode) (RGBstacking method).

The EL material that structures the EL layer differs depending on theluminescing color of the EL layer. Therefore, in the color displaysystem that employs three kinds of El elements corresponding to thecolors R (red), G (green), and B (blue), the three kinds of EL elementsof the EL layer corresponding to RGB each may deteriorate at differentrates. In this case, the luminance of the EL elements that correspond toRGB becomes dissimilar, respectively, as time passes. Consequently, animage having a desirable color cannot be displayed on the EL display.

SUMMARY OF THE INVENTION

The present invention has been made in view of the above, and thereforehas an object to provide an EL display capable of performing a clear anddesirable color display by suppressing a reduction in luminance of an ELelement even if an EL layer is deteriorated.

The EL display of the present invention has a sensor portion fordetecting a luminance of a portion for displaying an image of the ELdisplay (display portion) and revising the luminance to a desirablevalue. The sensor portion includes one or a plurality of pixels. It isto be noted that the pixel(s) of the sensor portion will hereinafter bereferred to as sensor pixel(s) throughout this specification.

The sensor pixel(s) is composed of an EL element and a light receivingdiode that detects the amount of change in the luminance of the ELelement. It is to be noted that throughout this specification, the ELelement of the sensor pixel(s) will hereinafter be referred to as asensor EL element.

The sensor EL element has the same structure as that of the EL element(hereinafter referred to as display EL element) of the pixel(hereinafter referred to as display pixel) of the display portion. Atleast a material that constructs a pair of electrodes and a materialthat constructs a lamination structure of an EL layer and the EL layerare the same, respectively.

Then, a signal, which is the same as a signal inputted to an arbitrarilyselected display EL element, is fed to the sensor EL element. In thisspecification, the input of a signal to the EL element (display ELelement and sensor EL element) means that an electric potential of thesignal is applied to one of the electrodes of the EL element, and an ELdrive voltage is applied to the EL layer. Here, the EL drive voltage isthe electric potential difference between the electric potential of thesignal applied to one of the electrodes of the EL element and theconstant electric potential applied to the other electrode thereof.

Thus, an equivalent voltage is applied to the EL layers of the sensor ELelement and the arbitrarily selected display EL element, whereby thedeterioration rates of the EL layers are nearly equivalent. Therefore,the luminance of the sensor EL element and the luminance of the displayEL element maintain almost equivalent states even as time elapses.

Light emitted by the sensor EL element, on one hand, is irradiated tothe light receiving diode of the senor pixel. Then, the light receivingdiode detects the luminance of the sensor EL element. On the basis ofthe information of the luminance of the sensor EL element that wasdetected, the luminance of the display EL element is revised, and theluminance of the sensor EL element is also revised at the same time.

By adopting the above structure, the present invention has made itpossible for the EL display to perform a clear and desirable colordisplay by suppressing the reduction in luminance of the EL element evenif the EL layer is deteriorated.

The EL display of the present invention may be of a color display systemthat employs a display EL element emitting white light, or a colordisplay system that employs display EL elements corresponding to thecolors RGB, respectively. In case of the color display system thatemploys the display EL elements corresponding to each of the colors RGB,it is preferable that the sensor pixels corresponding to each of thecolors RGB are provided in the sensor portion. However, the presentinvention is not limited to the structure thereof. It may be a structurein which the sensor pixels, which correspond to either 1 or 2 colors ofthe RGB colors, are provided in the sensor portion. In particular, it iseffective to provide the sensor pixel that corresponds to the color ofwhich the deterioration of the EL layer is remarkable in the sensorportion to thereby display an image having a desirable color.

It is further preferable that the display EL element and the sensor ELelement are formed at the same time under the same conditions. Thedeterioration rates of the EL layers of the display EL element and thesensor EL element can be made equivalent by adopting the abovestructure. Therefore, the luminance of the sensor EL element that willbe detected by the light receiving diode becomes equivalent wraith theluminance of the display EL element, to thereby detect the change in theluminance of the display EL element more accurately. Thus, it becomespossible to revise the luminance of the display EL element to adesirable value.

Furthermore, when the sensor portion is formed simultaneously with thedisplay portion on the substrate, as the manufacturing process of the Eldisplay, only the process of forming the light receiving diode has to beadded to the manufacturing process in the case where the sensor portionis not provided. Therefore, there is no need to remarkably increase thenumber of manufacturing processes, thereby making it possible tosuppress the number of manufacturing processes.

It is to be noted that a portion of the display portion may be used asthe sensor portion. That is, among the pixels of the display portion,one or a plurality of pixels that are arbitrarily selected may beemployed as sensor pixels and the rest of the pixels may be employed asdisplay pixels. In this case, the size of the EL display can besuppressed because the space for the provision of the sensor portion canbe omitted compared with the case of not including the sensor portion inthe display portion.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings:

FIG. 1 is a schematic diagram of the top of an EL display of the presentinvention;

FIG. 2 is a circuit diagram of an EL display of the present invention;

FIG. 3 is a circuit diagram of a sensor pixel of an EL display of thepresent invention;

FIG. 4 is a circuit diagram of a display pixel of an EL display of thepresent invention;

FIG. 5 is a timing chart when an EL display of the present invention isdriven by a digital method;

FIG. 6 is a block diagram of a correction circuit of an EL display ofthe present invention;

FIG. 7 is a schematic diagram of the top of an EL display of the presentinvention;

FIG. 8 is a timing chart when an EL display of the present invention isdriven by an analog method;

FIG. 9 is a block diagram of a video signal correction circuit of an ELdisplay of the present invention;

FIGS. 10A to 10E are diagrams showing a process of manufacturing an ELdisplay of the present invention;

FIGS. 11A to 11D are diagrams showing the process of manufacturing theEL display of the present invention;

FIGS. 12A to 12C are diagrams showing the process of manufacturing theEL display of the present invention;

FIGS. 13A and 13B are diagrams showing the process of manufacturing theEL display of the present invention;

FIG. 14 is a cross sectional diagram of an EL display of the presentinvention;

FIG. 15 is a circuit diagram of a sensor pixel of an EL display of thepresent invention;

FIG. 16 is a cross sectional diagram of an EL display of the presentinvention;

FIGS. 17A and 17B are external views of an EL display of the presentinvention;

FIGS. 18A and 18B are external views of an EL display of the presentinvention;

FIG. 19 is a cross sectional diagram of a display pixel of an EL displayof the present invention;

FIGS. 20A and 20B are a top view and a circuit diagram, respectively, ofa display pixel of an EL display of the present invention;

FIG. 21 is a cross sectional diagram of a display pixel of an EL displayof the present invention;

FIGS. 22A to 22C are circuit diagrams of a display pixel of an ELdisplay of the present invention;

FIGS. 23A to 23F are diagrams showing examples of electronic equipmentusing an EL display of the present invention;

FIGS. 24A and 24B are diagrams of electronic equipments using an ELdisplay of the present invention; and

FIG. 25 is a cross sectional diagram of an EL display of the presentinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

An embodiment mode of the present invention ill be explained withreference to FIGS. 1 to 6.

Shown in FIG. 1 is a top view of an EL display, which is a portion of asemiconductor display device of the present invention. It is to be notedthat in the embodiment mode of the present invention, an explanationwill be made on an EL display for performing color display that isdriven by a digital method. However, the driving method of the ELdisplay of the present invention is not limited to the digital method,and the EL display may be driven by an analog method. In addition,although an explanation is made in the embodiment mode on the EL displayfor performing color display, the EL display of the present inventionmay performs not only color display, but also monochrome display.

As shown in FIG. 1, there is provided a display portion 101, a sourcesignal line driver circuit 102, a gate signal line driver circuit 103,and a sensor portion 106. The source signal line driver circuit 102 iscomposed of a shift register 102 a, a latch (A) 102 b, and a latch (B)102 c.

The sensor portion 106 has sensor pixels 104 (R sensor pixel 104 a, Gsensor pixel 104 b, and B sensor pixel 104 c) that correspond to thecolors RGB, respectively. Note that an EL display of a color displaysystem that employs three kinds of EL elements corresponding to thecolors RGB is illustrated in the embodiment mode. However, the presentinvention is not limited thereto, and an EL display of a color displaysystem that employs an EL element emitting white light may be used.Further, in the embodiment mode, although the sensor portion 106 has 3sensor pixels that correspond to the colors RGB, respectively, thepresent invention is not limited thereto. Only sensor pixels thatcorrespond to 1 or 2 colors of the colors RGB may be provided in thesensor portion.

A detailed circuit diagram of the displace portion 101 and the sensorportion 106 is shown in FIG. 2. Source signal lines (S1 to Sx), powersource supply lines (V1 to Vx), and gate signal lines (G1 to Gy) areprovided in the display portion 101. Note that the sensor portion 106and the display portion 101 are provided on the same substrate in theembodiment mode. However, the present invention is not limited thereto.The structure may be such that the sensor portion and the displayportion are provided on different substrates and connected by an FPC orthe like.

The display portion 101 includes a plurality of display pixels 105. Thedisplay pixels 105 each have any one of the source signal lines (S1 toSx), any one of the power source supply lines (V1 to Vx), and any one ofthe gate signal lines (G1 to Gy). There are 3 types of display pixels105: a display pixel for displaying the color R; a display pixel fordisplaying the color G; and a display pixel for displaying the color B.

A source signal line Sp (where p is an arbitrary number between 1 andx), a power source supply line Vp, and a gate signal line Gq (where q isan arbitrary number between 1 and y) are contained in an arbitrarilyselected display pixel (p, q) of the display pixels for displaying thecolor R. Also, similar to the display pixel (p, q) for displaying thecolor R, the source signal line Sp, the power source supply line Vp, andthe gate signal line Gq are contained in the R sensor pixel 104 a.

Though not shown in the figure, similarly the same source signal line,power source supply line, and gate signal line that are included in anarbitrarily selected display pixel for displaying the color G are alsocontained in the G sensor pixel 104 b. Likewise not shown in the figure,the same source signal line, power source supply line, and gate signalline that are contained in an arbitrarily selected display pixel fordisplaying the color B are also contained in the B sensor pixel 104 c.

A detailed structure of the sensor pixels 104 a to 104 c is shown inFIG. 3. A region that is surrounded by a dotted line is the sensor pixel104. Contained in the sensor pixel 104 are a source signal line S (anyone of the lines between S1 and Sx), a power source supply line V (anyone of the lines between V1 and Vx), and a gate signal line G (any oneof the lines between G1 and Gy).

In addition, the sensor pixel 104 (104 a to 104 c) has a switching TFT130, an EL driving TFT 131, and a sensor EL element 132. A capacitor 133is provided in the structure of FIG. 3, but the structure mal be formedwithout the provision of the capacitor 133.

The sensor EL element 132 is composed of an anode, a cathode, and an ELlayer provided therebetween. When the anode is connected to a drainregion of the EL driving TFT 131, in other words, when the anode is apixel electrode, the cathode serving as an opposing electrode is held ata predetermined electric potential (opposing electric potential). On theother hand, when the cathode is connected to the drain region of the ELdriving TFT 131, in other words, when the cathode is the pixelelectrode, then the anode serving as the opposing electrode is held at apredetermined electric potential (opposing electric potential).

A gate electrode of the switching TFT 130 is connected to the gatesignal line G. One of a source region and a drain region of theswitching TFT 130) is connected to the source signal line S, and theother is connected to a gate electrode of the EL driving TFT 131.

One of a source region and the drain region of the EL driving TFT 131 isconnected to the power source supply line V, and the other is connectedto the sensor EL element 132. The capacitor 133 is provided so as to beconnected to the gate electrode of the EL driving TFT 131 and the powersource supply line V.

Further, the sensor pixel 104 has a reset TFT 134, a buffer TFT 135, anda light receiving diode 136.

A gate electrode of the reset TFT 134 is connected to a reset signalline RL. A source region of the reset TFT 134 is connected to a sensorpower source line VB and a drain region of the buffer TFT 135. Thesensor power source line VB is constantly held at a fixed electricpotential (standard electric potential). Further, a drain region of thereset TFT 134 is connected to the light receiving diode 136 and a gateelectrode of the buffer TFT 135.

A source region of the buffer TFT 135 is connected to a sensor outputwiring FL. The sensor output wiring FL is further connected to aconstant-current power source 137 and a fixed current constantly flowstherein. Further, the drain region of the buffer TFT 135 is connected tothe sensor power source line VB which is constantly maintained at afixed standard electric potential. The buffer TFT 135 functions as asource follower.

Although not shown in the figure, the light receiving diode 136 iscomposed of a cathode, an anode, and a photoelectric converting layerprovided therebetween.

Shown in FIG. 4 is a detailed structure of the display pixel 105. Anarea surrounded by a dotted line is the display pixel 105. The sourcesignal line S (any one of the lines between S1 and Sx), the power sourcesupply line V (any one of the lines between V1 and Vx), and the atesignal line G (any one of the lines between G1 and Gy) are contained inthe display pixel 105.

Similar to the sensor pixel 104, the display pixel 105 has a switchingTFT 140, an EL driving TIT 141, and a display EL element 142. Thedisplay EL element 142 has the same structure as that of the sensor ELelement 132 that is shown in FIG. 3. To be more specific, the display ELelement 142 and the sensor EL element 132 each have an EL layersandwiched between a pair of electrodes. In addition, the materialconstructing the pair of electrodes and the laminate structure of the ELlayer are at least respectively the same for both the EL elements. Inparticular, when the color of light emitted by the sensor EL element 132and the display EL element 142 is the same, then the material (ELmaterial) that forms the EL layer is also the same.

The display EL element 142 is composed of an anode, a cathode, and an ELlayer provided therebetween. When the anode is connected to a drainregion of the EL driving TFT 141, in other words, when the anode is apixel electrode, the cathode serving as an opposing electrode is held ata predetermined electric potential (opposing electric potential). On theother hand, when the cathode is connected to the drain region of the ELdriving TFT 141, in other words, when the cathode is the pixelelectrode, then the anode serving as the opposing electrode is held at apredetermined electric potential (opposing electric potential).

Further, a capacitor 143 is provided in the structure of FIG. 4, but thestructure may be formed without the provision of the capacitor 143.

A gate electrode of the switching TFT 140 is connected to the gatesignal line G. One of a source region and a drain region of theswitching TFT 140 is connected to the source signal line S, and theother is connected to a gate electrode of the EL driving TFT 141.

One of a source region and the drain region of the EL driving TFT 141 isconnected to the power source supply line V, and the other is connectedto the display EL element 142. The capacitor 143 is provided so as to beconnected to the gate electrode of the EL driving TFT 141 and the powersource supply line V.

Next, a description will be made on a driving method of the EL displayof the embodiment mode.

FIG. 1 is referenced. In the source signal line driver circuit 102, aclock signal (CLK) and a start pulse (SP) are inputted to the shiftregister 102 a. The shift register 102 a sequentially generates timingsignals on the basis of the clock signal (CLK) and the start pulse (SP)to thereby sequentially feed the timing signals to downstream circuits.

The timing signals from the shift register 102 a are current-amplifiedby a buffer (not shown) or the like, and the current-amplified timingsignals may be sequentially fed to the downstream circuits. A largenumber of circuits or elements are connected to the wiring through whichthe timing signals are fed, so that the load capacitance (parasiticcapacitance). The buffer is provided to prevent the sharpness of therise or fall of the timing signals from being reduced by this large loadcapacitance.

The timing signals from the shift register 102 a are then fed to thelatch (A) 102 b. The latch (A) 102 b has a plurality of stages oflatches for processing n-bit digital video signals. The latch (A) 102 bsequentially writes in and holds the n-bit digital video signalsincluding image information upon input of the timing signals.

Note that the digital video signals may be sequentially fed to theplural stages of the latches of the latch (A) 102 b when the digitalvideo signals are taken in by the latch (A) 102 b. However, the presentinvention is not limited to this structure. A so-called division drivemay be performed in which the plural stages of latches of the latch (A)102 b are divided into a number of groups and then the digital videosignals are parallely fed to the respective groups at the same time. Itis to be noted that the number of groups at this point is called adivision number. For example, if the latches are grouped into 4 stageseach, then it is called a 4-branch division drive.

The time necessary to complete writing of the digital video signals intoall the stages of the latches of the latch (A) 102 b is called a lineperiod. In other words, the line period is defined as a time intervalfrom the start of writing the digital video signals into the latch ofthe leftmost stage to the end of writing the digital video signals intothe latch of the rightmost stage in the latch (A) 102 b. In practice, aline period may be a period in which a horizontal return period is addedto the above line period.

After the completion of one line period, a latch signal is fed to thelatch (B) 102 c. At this moment, the digital video signals written inand held by the latch (A) 102 b are sent all at once to the latch (B)102 c to be written in and held by all the stages of latches thereof.

Sequential writing-in of digital video signals on the basis of thetiming signals from the shift register 109 a is again carried out to thelatch (A) 102 b after it has completed sending the digital video signalsto the latch (B) 102 c.

During this second time one line period, the digital video signalswritten in and held by the latch (B) 102 b are inputted to source signallines.

On the other hand, the ate signal line driver circuit 103 is composed ofa shift register and a buffer (both not shown in the figure). Dependingon the situation, the gate signal line driver circuit 103 may have alevel shifter beside the shift register and the buffer.

In the gate signal line driver circuit 103, the timing signals from theshift register (not shown in the figure) are fed to the buffer (notshown in the figure) to be fed to corresponding gate signal lines (alsoreferred to as scanning lines). The gate signal lines are connected tothe gate electrodes of the switching TFTs of one line, and all theswitching TFTs of one line have to be turned ON simultaneously.Therefore, the use of a buffer with a large electric current capacity isrequired.

It is to be noted that the structure, the driving method, and the numberof the source signal line driver circuit 102 and the gate signal linedriver circuit 103 are not limited to the structure in the embodimentmode.

Shown in FIG. 5 is a timing chart illustrating a case where the ELdisplay of the present invention is driven by the digital method toperform a display.

First, a 1 frame period (F) is divided into an “n” number of sub-frameperiods (SF1 to SFn). Note that a period in which all the pixels in thepixel portion display 1 image is referred to as the 1 frame period (F).

The provision of 60 or more frame periods within one second by the ELdisplay is preferred. The glimmering of images such as flickering may bevisually suppressed by providing the number of images displayed in onesecond to be 60 or more.

Note that a period in which 1 frame period is divided into a pluralityof periods is referred to as sub-frame period (SF). As the number oftones increase, the number of sub-frame periods in 1 frame period alsoincreases.

The subframe periods are divided into address periods (Ta) and sustainperiods (Ts). The address period is a period required for inputtingdigital video signals into all of the pixels during one subframe period,and the sustain period (also referred to as a turn on period) denotes aperiod in which the EL element is made to either emit light or not tothereby perform display by the digital video signals inputted to thepixels in the address period.

The address periods (Ta) of SF1 to SFn are Ta1 to Tan, respectively. Thesustain periods (Ts) of SF1 to SFn are Ts1 to Tsn, respectively.

The electric potential of the power source supply lines (V1 to Vx) ismaintained at a predetermined electric potential (power source electricpotential).

First, in the address period Ta, the electric potential of the opposingelectrodes of both the display EL element 142 and the sensor EL element132 is maintained at a level equivalent to the power source electricpotential.

Then, a gate signal is fed to the gate signal line G1. Among the pluralnumber of switching TFTs 140 of the display pixels 105 and the pluralnumber of switching TFTs 130 of the sensor pixels 104, all the switchingTFTs connected to the gate signal line G1 are turned into the ON state.Note that throughout this specification, a TFT in the ON state isreferred to as driving of a TFT.

Next, the digital video signals from the source signal line drivercircuit 102 are fed to the source signal lines (S1 to Sx) in the statethat all the switching TFTs connected to the gate signal line G1 areturned into the ON state. The digital video signals have the information[0] or [1]. The digital video signals [0] and [1] are signals where onehas a “Hi” (High) voltage while the other has an “Lo” (Low) voltage.

Then via the switching TFTs that are in the ON state, the digital videosignals that are fed to the source signal lines (S1 to Sx) are fed tothe gate electrode of the EL driving TFT, which is connected to thesource region or the drain region of the switching TFTs.

Next, the gate signal is fed to the gate signal line G2, whereby ail theswitching TFTs 1501 that are connected to the gate signal line G2 turninto the ON state. Among the plural number of switching TFTs 140 of thedisplay pixels 105 and the plural number of switching TFTs 130 of thesensor pixels 104, all the switching TFTs connected to the gate signalline G2 are turned into the ON state.

The digital video signals from the source signal line driver circuit 102are then fed to the source signal lines (S1 to Sx) in the state that allthe switching TFTs connected to the gate signal line G2 are turned intothe ON state. Then via the switching TFTs that are in the ON state, thedigital video signals that are fed to the source signal lines (S1 to Sx)are fed to the gate electrode of the EL driving TFT, which is connectedto the source region or the drain region of the switching TFTs.

The above-described operation is repeated until the gate signal is fedto the gate signal line Gy to thereby input the digital video signals toall the display pixels 105 and the sensor pixels 104. A period until thecompletion of inputting the digital video signals to all the displaypixels 105 and the sensor pixels 104 is the address period. Note thatthe lengths of the respective address periods (Ta1 to Tan) of the nnumber of sub-frame periods are all the same.

Upon the completion of the address period Ta, a sustain period begins.In the sustain period, the electric potential of all the opposingelectrodes of the EL elements is set to a level where it has an electricpotential difference with the power source electric potential to theextent that the EL element emits light when the power source electricpotential is applied to the pixel electrode.

Thereafter, in the sustain period, all the switching TFTs of the displaypixels 105 and the sensor pixels 104 are turned into the OFF state. Thedigital video signal fed to the display pixels 105 and the sensor pixels104 is then fed to the gate electrode of the EL driving TFT of each ofthe pixels.

In the embodiment mode, when the digital video signal has theinformation [0], then the EL driving TFT is turned into the OFF state.Therefore, the pixel electrode of the EL element is in the state ofbeing maintained at the electric potential of the opposing electrode. Asa result, the EL element of the pixel to which the digital video signalhaving the information [0] is inputted does not emit light.

On the other hand, when the digital video signal has the information[1], then the EL driving TFT is turned into the ON state in theembodiment mode. Therefore, the power source electric potential isapplied to the pixel electrode of the EL element. As a result, the ELelement of the pixel to which the digital video signal having theinformation [1] is inputted emits light.

Thus, the EL element either emits light or not depending on theinformation of the digital video signal to the pixels, whereby thepixels perform display.

Upon completion of the sustain period, 1 subframe period ends. Then thenext subframe period appears and turns into an address period again. Atthe point the digital video signals have been fed to all the pixels, asustain period begins again. It is to be noted that the order ofappearance of the sub-frame periods is arbitrary.

The same operation is repeated in the rest of the sub-frame periods tothereby perform display. Upon the completion of the “n” number ofsub-frame periods. 1 frame period ends.

Further, in the present invention, a ratio of the lengths of the “n”number of sustain periods Ts1, . . . , Tsn is expressed as Ts1: Ts2:Ts3: . . . : Ts(n−1): Tsn=2⁰: 2⁻¹: 2⁻²: . . . : 2^(−(n−2)): 2^(−(n−1)).

The gradation of each pixel is determined by which subframe period isselected for light emission during one frame period. For example, ifn=S, and the luminance of pixels having light emitted during all of thesustain periods is taken as 100%, then in case of the pixels emittinglight in Ts1 and Ts2, the luminance is expressed as 70%, and hen Ts3,Ts5, and Ts8 are selected, the luminance can be expressed as 16%.

Note that in the embodiment mode, the EL element did not emit lightbecause the electric potential of the opposing electrode was maintainedat an electric potential that is equivalent to the power source electricpotential in the address period. However, the present invention is notlimited to this structure. An electric potential difference to theextent that EL element emit light when the power source electricpotential is applied to the pixel electrode is constantly providedbetween the opposing electric potential and the power source electricpotential. Thus, the address period, similarly to the display period,may also perform display. However, in this case, all the subframeperiods actually become periods performing display, and therefore, thelengths of the subframe periods are set at SF1: SF2: SF3: . . . :SF(n−1): SFn=2⁰: 2⁻¹: 2⁻²: . . . : 2^(−(n−2)): 2^(−(n−1)). By adoptingthe above structure, a high luminance image can be attained comparedwith the driving method where the address periods do not emit light.

As explained above, simultaneously with the display of an image in thedisplay portion depending on the luminescent or non-luminescent state ofthe display EL elements, similar to the display EL elements, the sensorEL elements become either luminescent or non-luminescent state.

Next, an explanation will be made on the mechanism of the lightreceiving diode 136 detecting the luminance of the sensor EL element 132in the sensor portion 106.

It is desirable that one of the reset TFT 134 and the buffer TFT 135 ofthe sensor pixel 104 is an n-channel TFT, and the remaining one is ap-channel TFT.

First, the reset TFT 134 is turned into the ON state depending on areset signal that is fed to the rest signal line RL. Therefore, thestandard electric potential of the sensor power source line VB isapplied to gate electrode of the buffer TFT 135. The source region ofthe buffer TFT 135 is connected to the constant-current power source viathe sensor output wiring FL, whereby the electric potential differenceV_(GS) of the gate electrode and the source region of the buffer TFT 135is constantly at a fixed value. Accordingly the source region of thebuffer TFT 135 is held at an electric potential where V_(GS) issubtracted from the standard electric potential. Note that in thisspecification, a period in which the reset TFT 134 is in the ON state isreferred to as a reset period.

Next, the electric potential of the reset signal that is fed to thereset signal line RL is changed, whereby the reset TFT 134 is turnedinto the OFF state. Therefore, the standard electric potential of thesensor power source line PUB is not applied to the gate electrode of thebuffer TFT 135. Note that a period in which the reset TFT 134 is in theOFF state is referred to as a sample period in this specification.

In case of the EL display being driven by the digital method, the sampleperiod is longer than the address period Ta and overlaps the sustainperiod Ts in which the sensor EL element 132 is emitting light.

The irradiation of the light generated from the sensor EL element 132 tothe light receiving diode 136 makes a current flow in the lightreceiving diode 136. Therefore, the fixed electric potential of the gateelectrode of the buffer TFT 135, in the reset period changes in thesample period. The amount of the change in the electric potential willalternates on the basis of the size of the current flowing in the lightreceiving diode 136.

The current flowing in the light receiving diode 136 is proportional tothe strength of the light irradiated thereto. In other words, comparedwith when the luminance of the sensor EL element 132 is high and whenthe luminance thereof is low, a larger current flows to the lightreceiving diode 136 when the luminance thereof is high. Consequently,the electric potential of the gate electrode of the buffer TFT 135undergoes a large change when the luminance of the sensor EL element 132is high compared with when the luminance thereof is low.

Because the electric potential difference V_(GS) of the source regionand the gate electrode of the buffer TFT 135 is always a fixed value,the electric potential of the source region of the buffer TFT 135 ismaintained at an electric potential in which V_(GS) is subtracted fromthe electric potential of the gate electrode thereof. Thus, when theelectric potential of the gate electrode of the buffer TFT 135 chances,the electric potential of the source region of the buffer TFT 135changes together therewith.

The electric potential of the source region of the buffer TFT 135 isapplied to the sensor output wiring FL to thereby be fed to a correctioncircuit as a sensor output signal.

Shown in FIG. 6 is the block diagram of a correction circuit 201. Thecorrection circuit 201 may be provided on the same substrate with thedisplay portion 101 or the sensor portion 106. Further, it may beprovided on an IC chip and be connected to the sensor portion 106 by anFPC or the like.

The correction circuit 201 is composed of an A/D converter circuit 202,a arithmetic circuit 203, a correction memory 204, and a D/A convertercircuit 205. Note that although the structure of FIG. 6 shows a casewhere the correction memory 204 is constructed as a part of thearithmetic circuit 203, the correction memory 204 and the arithmeticcircuit 203 may be provided separately.

The sensor output signal from the sensor output wiring FL is fed to theA/D converter circuit 202 to thereby be converted into a digital sensoroutput signal and be outputted therefrom. The digital sensor outputsignal outputted from the A/D converter circuit 202 is then fed to thearithmetic circuit 203.

When the sensor EL element 132 has an ideal luminance, the data of thedigital sensor output signal (correction standard data) that is to befed to the arithmetic circuit 203 is stored in the correction memory204.

The arithmetic circuit 203 compares the digital sensor output signalthat was actually fed to the arithmetic circuit 203 with the correctionstandard data stored in the correction memory 204. Then the arithmeticcircuit 203 calculates, from the difference between the actual sensoroutput signal and the correction standard data that were compared, thelevel of the electric potential (power source electric potential) of thepower source supply line V necessary for the display EL element 142 andthe sensor El element 132 to obtain an ideal luminance. Thereafter, thearithmetic circuit 203 feeds the digital correction signal having theinformation of the level of the power source electric potential to theD/A converter circuit 205.

The digital correction signal that is fed to the D/A converter circuit205 is converted into an analog signal to thereby be fed to an EL powersource 206. The EL power source 206 applies an electric potential hoselevel is determined by the inputted analog correction signal to thepower source supply lines (V1 to Vx). In case the luminance of the ELelement is reduced, the correction mechanism works by regulating thepower source electric potential of the power source supply lines so asto supplement the reduction thereof to thereby enhance the luminance ofthe EL element.

Note that when the EL display employs the three kinds of EL elementscorresponding to the colors RGB, it is necessary to provide thecorrection circuit 201 and the EL power source 206 to each of the colorsto be revised. In other words, in case of revising each of the colorsRGB, the provision of 3 correction circuits 201 and 3 EL power sources206 is necessary.

Furthermore, when the EL display employs an EL element emitting a singlecolor such as white, blue, or blue-preen, the provision of thecorrection circuit 201 and the EL power source 206 may be one of each,or the provision thereof max; be for each color to be revised. Thedeterioration rate of the EL layer differs depending on the wavelengthof the light irradiated thereto. Therefore, in case of the EL displayemploying the EL element emitting white light and a color filter, byproviding the correction circuit 201 and the EL power source 206 to eachof the colors to be revised, a more accurate correction can be made tothe luminance of the EL element corresponding to each of the colors. Asa result, a clearer image of a desirable color as well can be displayed.

In the present invention, by adopting the above structure, the displayEL element 142 and the sensor EL element 132 are capable of having anideal luminance, thereby making it possible for the EL display toperform a clear and desirable color display even if the EL layer in theEL display deteriorates.

Note that although the sensor portion has one of the sensor pixelscorresponding to the respective colors RGB in the embodiment mode, thepresent invention is not limited thereto. A plurality of sensor pixelscorresponding to each of the colors may be provided.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the present invention are explained below.

Embodiment 1

An EL display of the present invention driven by an analog method isexplained in Embodiment 1 using FIGS. 7 to 9.

Shown in FIG. 7 is a top view of an EL display, which is a portion of asemiconductor display device of the present invention. In Embodiment 1,an explanation will be made on an EL display for performing colordisplay. However, the EL display of the present invention not onlyperforms color display but may also perform monochrome display.

As shown in FIG. 7, there is provided a displays portion 301, a sourcesignal line driver circuit 302, a gate signal line driver circuit 303,and a sensor portion 306. The source signal line driver circuit 302 iscomposed of a shift register 302 a, a level shifter 302 b, and asampling circuit 302 c.

The sensor portion 306 has sensor pixels 304 (R sensor pixel 304 a, Gsensor pixel 304 b, and B sensor pixel 304 c) that correspond to thecolors RGB, respectively. Note that an EL display of a color displaysystem that employs three kinds of EL elements corresponding to thecolors RGB is illustrated in Embodiment 1. However, Embodiment 1 is notlimited thereto, and an EL display of a color display system thatemploys an EL element emitting white light may be used. Further,although the sensor portion 306 shown in Embodiment 1 has 3 sensorpixels that correspond to the colors RGB, respectively, the presentinvention is not limited thereto. Only sensor pixels that correspond to1 or 2 colors of the colors RGB may be provided in the sensor portion.

The detailed structure of the display portion 301 and the sensor portion306 is the same as for a case of driving by a digital method, andtherefore, FIG. 2 is referenced. Note that the display portion 301, thesensor portion 306, the R sensor pixel 304 a, the G sensor pixel 304 b,and the B sensor pixel 304 c, all of FIG. 7, correspond to the displayportion 101, the sensor portion 106, the R sensor pixel 104 a, the Gsensor pixel 104 b, and the B sensor pixel 104 c, respectively, of FIG.2.

Note that, in Embodiment 1, the sensor portion and the display portionare formed on the same substrate, but the present invention is notlimited thereto. A structure may be such that the sensor portion and thedisplay portion are formed on different substrates and connected by aconnector such as an FPC.

The display portion 301 includes a plurality of display pixels. Notethat the display pixels in Embodiment 1 correspond to the display pixels105 in FIG. 2. The display pixels 105 each have any one of source signallines (S1 to Sx), any one of power source supply lines (V1 to Vx), andany one of gate signal lines (G1 to Gy). There are 3 types of displaypixels: a display pixel for displaying the color R; a display pixel fordisplaying the color G; and a display pixel for displaying the color B.

A source signal line Sp (where p is an arbitrary number between 1 andx), a power source supply line Vp, and a gate signal line Gq (where q isan arbitrary number between 1 and y) are contained in an arbitrarilyselected display pixel (p, q) for displaying the color R. Also, similarto the display pixel (p, q), the source signal line Sp, the power sourcesupply line Vp, and the gate signal line Gq are contained in the Rsensor pixel 304 a.

Also, the same source signal line, power source supply line, and gatesignal line that are included in an arbitrarily selected display pixelfor displaying the color G are also contained in the G sensor pixel 304b. Further, the same source signal line, power source supply line, andgate signal line that are contained in an arbitrarily selected displaypixel for displaying the color B are also contained in the B sensorpixel 304 c.

The structures of the display pixel and the sensor pixel 304 are thesame as for the case of driving by the digital method of FIG. 3 and FIG.4, and therefore the embodiment mode may be referenced for anexplanation of the structures.

Next, a description will be made on a driving method of an EL display ofEmbodiment 1.

FIG. 7 is referenced. In the source signal line driver circuit 302, aclock signal (CLK) and a start pulse (SP) are inputted to the shiftregister 302 a. The shift register 302 a sequentially generates timingsignals on the basis of the clock signal (CLK) and the start pulse (SP)to thereby sequentially feed the timing signals to downstream circuits.

A timing signal from the shift register 302 a has its voltage amplitudemade larger in the level shifter 302 b, and is inputted to the samplingcircuit 302 c. The sampling circuit 302 c, in synchronous with thetiming signal, then samples the signal having analog image information(analog video signal) in accordance with an analog switch, and thesampled signal is inputted to a corresponding source signal line.

Note that the source signal line driver circuit 302 may have a buffer. Alarge number of circuits or elements are connected to the wiring throughwhich the timing signals are fed, so that the load capacitance(parasitic capacitance) due to those circuits or elements is large. Thebuffer is effective to prevent the sharpness of the rise or fall of thetiming signals from being reduced due to this large load capacitance.

On the other hand, the gate signal line driver circuits 303 each have ashift register and a buffer (neither shown in the figures). Further, thegate signal line driver circuits 303 also may have level shiftercircuits other than a shift register and a buffer.

The timing signal is supplied to the buffer (not shown in the figure)from the shift register (not shown in the figure) in the gate signalline driver circuit 303, and is then supplied to a corresponding gatesignal line (also referred to as a scanning line). The gate electrodesof the switching TFT for one line are connected to the gate signal line,and all of the switching TFTs for one line must be turned ONsimultaneously. Therefore, a buffer capable of handling a large electriccurrent flow is used.

Note that the number of the source signal line driver circuits 302 andthe gate signal line driver circuits 303, the circuit structures, andthe methods of driving the circuits are not limited to the constitutionshown in Embodiment 1.

Next, a timing chart for a case of driving the EL display of the presentinvention by the analog method is shown in FIG. 8. A period from theselection of one ate signal line in accordance with a gate signal untila different gate signal line is next selected is referred to as one lineperiod (L). Further, a period from display of one image until display ofthe next image is referred to as one frame period (F). When there are ygate signal lines, there are y line periods (L1 to Ly) formed within oneframe period.

First, power source supply lines (V1 to Vx) are maintained at apredetermined electric power source potential. An opposing electrode isalso maintained at a predetermined electric potential. The electricpotential of the opposing electrode has an electric potential differencewith the electric power source potential to the extent that an ELelement emits light when the electric power source potential is appliedto a pixel electrode.

A selection signal is inputted to a gate signal line G1 in the firstline period L1 from the ate signal line driver circuit 303. The sampledanalog video signal is then inputted to source signal lines (S1 to Sx).All of the switching TFTs connected to the gate signal line G1 is turnedON in accordance with the selection signal, and therefore, the analogvideo signal inputted to the source signal lines is inputted to the gateelectrodes of the EL driving TFTs through the switching TFTs.

The amount of electric current flowing in a channel forming region ofthe EL driving TFT is controlled by the height (voltage) of the electricpotential of the signal inputted to its gate electrode. The height ofthe electric potential of the pixel electrode of the EL element istherefore determined by the electric potential of the analog signalinputted to the gate electrode of the EL driving TFT. The EL element isthen controlled by the electric potential of the analog video signal andemits light.

The above-stated operations are repeated, and when the analog videosignal is inputted to the source signal lines (S1 to Sx), the first lineperiod L1 ends. Note that the period until completion of analog videosignal inputted to the source signal lines (S1 to Sx) may also be takentogether with a horizontal return period as one line period. The secondline period L2 then begins, and the selection signal is inputted to thegate signal line G2. Then, similar to the first line period L1, theanalog video signal is inputted to the source signal lines (S1 to Sx) inorder.

When the selection signal is inputted to all of the gate signal lines(G1 to Gy), all of the line periods (L1 to Ly) are completed. One frameperiod is complete when all of the line periods (L1 to Ly) are complete.Display is performed in all of the pixels within one frame period, andone image is formed. Note that all of the line periods (L1 to Ly) may betaken together with a vertical return period as one frame period.

The luminance of the EL elements is thus controlled in accordance withthe electric potential of the analog video signal inputted to the sourcesignal lines, as above. Gray-scale display is performed in accordancewith the control of luminance.

An explanation of how the luminance of display EL elements and theluminance of sensor EL elements are corrected in accordance with asensor output signal outputted from the sensor portion 306 is explainednext using FIG. 9. Note that a light receiving diode detects theluminance of the sensor EL elements in the sensor pixel shown in FIG. 7.The processes until the sensor output signal is inputted to a sensoroutput wiring is the same as for the case of the digital drive ELdisplay shown in the embodiment mode, and therefore, the explanation isomitted.

The sensor output signal having luminance information of the sensor ELelement detected by the light receiving diode is inputted to a videosignal correction circuit through a sensor output wiring FL in asampling period.

A block diagram of a video signal correction circuit 401 is shown inFIG. 9. The video signal correction circuit 401 may be formed on thesame substrate as the display portion 3(01 and the sensor portion 306,and it may also be formed on an IC chip and connected to the sensorportion 306 by an FPC or the like.

The video signal correction circuit 401 has an A/D converter circuit402, an arithmetic circuit 403, a correction memory 404, and a D/Aconverter circuit 405. Note that a structure for a case in which thecorrection memory 404 is a portion of the arithmetic circuit 403 isshown in FIG. 9, but the correction memory 404 and the arithmeticcircuit 403 may also be formed separately.

A signal generator 406 generates a signal having digital imageinformation (digital video signal), and this is inputted to thearithmetic circuit 403. Note that when the signal having imageinformation and output from the signal generator 406 (video signal) isanalog, the signal is first converted to a digital video signal by theA/D converter circuit and then is inputted to the arithmetic circuit403.

The sensor output signal is inputted to the A/D converter circuit 402from the sensor output wiring FL, is converted into a digital sensoroutput signal, and is then outputted. The digital sensor output signaloutputted from the A/D converter circuit 402 is then inputted to thearithmetic circuit 403.

When the display EL elements and the sensor EL elements have idealluminances, the digital sensor output signal data inputted to thearithmetic circuit 403 (correction standard date) is stored in thecorrection memory 404.

The arithmetic circuit 403 compares the actual digital sensor outputsignal inputted to the arithmetic circuit 403 with the correctionstandard data stored in the correction memory 404. Then, based upon thecomparative difference between the actual sensor output signal and thecorrection standard data, the digital video signal inputted to thearithmetic circuit 403 from the signal generator 406 is corrected. Notethat it is very important that the digital video signal after correctionat this time has the necessary electric potential in order to obtainideal luminance levels in the display EL elements and the sensor ELelements when converted to analog.

Note that a sensor output signal corresponding to each display color isinputted to the arithmetic circuit 403. For example, the three sensoroutput signals outputted from the R sensor pixel 304 a, the G sensorpixel 304 b, and the B sensor pixel 304 c are inputted to the arithmeticcircuit 403 in Embodiment 1. The digital video signal is corrected suchthat an analog video signal having a desired height electric potentialis sampled and inputted to pixels corresponding to each color (thedisplay pixels and the sensor pixels).

The corrected digital video signal is next inputted to the D/A convertercircuit 405 from the arithmetic circuit 403. The corrected digital videosignal inputted to the D/A converter circuit 405 is converted to analog,and is then inputted to the sampling circuit 302 c of the source signalline driver circuit 302 as an analog video signal. The analog videosignal has a necessary electric potential in order to obtain the idealluminance in the display EL elements and the sensor EL elements.

According to the above structure, in the present invention, the displayEL elements and the sensor EL elements can have ideal luminances, evenif the EL layer in the EL display deteriorates, and it becomes possibleto perform the desired color display with clarity.

Note that the sensor portion has one each of sensor pixels correspondingto R, G, and B in Embodiment 1, but the present invention is not limitedto this. A plurality of sensor pixels corresponding to each color mayalso exist.

Further, by correcting the electric potential of the analog video signalinputted to the display portion in the video signal correction circuit,the luminance of the EL elements is corrected with the analog drive ELdisplay of Embodiment 1. However, the present invention is not limitedto this. In addition to correcting the electric potential of the analogvideo signal in the video signal correction circuit, a correctioncircuit for correcting the electric power source potential may also beadded, similar to the digital drive EL display.

Embodiment 2

A method of manufacturing an EL display which uses the present inventionis explained using FIGS. 10A to 13B. A method of manufacturing a TFT ofa sensor portion is explained here, but it is also possible to similarlymanufacture a TFT of a display portion.

First, as shown in FIG. 10A, a base film 501 is formed to a thickness of300 nm on a glass substrate 500. A silicon oxynitride film is laminatedas the base film 501 in Embodiment 2. At this point, it is appropriateto set the nitrogen concentration to between 10 and 25 wt % in the filmcontacting the glass substrate 500. In addition, it is effective thatthe base film 501 has a thermal radiation effect, and a DLC(diamond-like carbon) film may also be provided.

Next, an amorphous silicon film (not shown in the figure) is formed witha thickness of 50 nm on the base film 501 by a known deposition method.Note that it is not necessary to limit to the amorphous silicon film,and another film may be formed provided that it is a semiconductor filmcontaining an amorphous structure (including a microcrystallinesemiconductor film). In addition, a compound semiconductor filmcontaining an amorphous structure, such as an amorphous silicongermanium film, may also be used. Further, the film thickness may bemade from 20 to 100 nm.

The amorphous silicon film is then crystallized by a known technique,forming a crystalline silicon film (also referred to as apolycrystalline silicon film or a polysilicon film) 502. Thermalcrystallization using an electric furnace, laser annealingcrystallization using a laser light, and lamp annealing crystallizationusing an infrared lamp exist as known crystallization methods.Crystallization is performed in Embodiment 2 using an excimer laserlight, which uses XeCl gas.

Note that pulse emission excimer laser light formed into a linear shapeis used in Embodiment 2, but a rectangular shape may also be used.Continuous emission arson laser light and continuous emission excimerlaser light can also be used.

In this embodiment, although the crystalline silicon film is used as theactive layer of the TFT, it is also possible to use an amorphous siliconfilm as the active layer.

Note that it is effective to form the active layer of the switching TFT,in which there is a necessity to reduce the off current, by an amorphoussilicon film, and to form the active layer of an EL driving TFT by acrystalline silicon film. Electric current flows with difficulty in theamorphous silicon film because the carrier mobility is low, and the offcurrent does not easily flow. In other words, the most can be made ofthe advantages of both the amorphous silicon film, through which currentdoes not flow easily, and the crystalline silicon film, through whichcurrent easily flows.

Next, as shown in FIG. 10B, a protective film 503 is formed on thecrystalline silicon film 502 with a silicon oxide film having athickness of 130 nm. This thickness may be chosen within the range of100 to 200 nm (preferably between 130 and 170 nm). Furthermore, otherfilms may also be used providing that they are insulating filmscontaining silicon. The protective film 503 is formed so that thecrystalline silicon film is not directly exposed to plasma duringaddition of an impurity, and so that it is possible to have delicateconcentration control of the impurity.

Resist masks 504 a and 504 b are then formed on the protective film 503,and an impurity element, which imparts n-type conductivity (hereafterreferred to as an n-type impurity element), is added through theprotective film 503. Note that elements residing in periodic table group15 are generally used as the n-type impurity element, and typicallyphosphorous or arsenic can be used. Note that a plasma doping method isused, in which phosphine (PH₃) is plasma-activated without separation ofmass, and phosphorous is added at a concentration of 1×10¹⁸ atoms/cm³ inEmbodiment 2. An ion implantation method, in which separation of mass isperformed, may also be used, of course.

The dose amount is regulated such that the n-type impurity element iscontained in an n-type impurity region (b) 505, thus formed by thisprocess, at a concentration of 2×10¹⁶ to 5×10¹⁹ atoms/cm³ (typicallybetween 5×10¹⁷ and 5×10¹⁸ atoms/cm³).

Next, as shown in FIG. 10C, the protective film 503 and the resist masks504 a and 504 b are removed, and an activation of the added n-typeimpurity elements is performed. A known technique of activation may beused as the means of activation, but activation is done in Embodiment 2by irradiation of excimer laser light (laser annealing). Of course, apulse emission excimer laser and a continuous emission excimer laser mayboth, be used, and it is not necessary to place any limits on the use ofexcimer laser light. The goal is the activation of the added impurityelement, and it is preferable that irradiation is performed at an energylevel at which the crystalline silicon film does not melt. Note that thelaser irradiation may also be performed with the protective film 503 inplace.

The activation by heat treatment (furnace annealing) may also beperformed along with activation of the impurity element by laser light.When activation is performed by heat treatment, considering the heatresistance of the substrate, it is good to perform heat treatment at onthe order of 450 to 550° C.

A boundary portion (connecting portion) with end portions of the n-typeimpurity region (b) 505, namely regions, in which the n-type impurityelement is not added, on the periphery of the n-type impurity region (b)505, is delineated by this process. This means that, at the point whenthe TFTs are later completed, extremely good connecting portion can beformed between LDD regions and channel forming regions.

Unnecessary portions of the crystalline silicon film are removed next,as shown in FIG. 10D, and island-shape semiconductor films (hereafterreferred to as active layers) 506 to 509 are formed.

Then, as shown in FIG. 10E, a gate insulating film 510 is formed,covering the active layers 506 to 509. An insulating film containingsilicon and with a thickness of 10 to 200 nm, preferably between 50 and150 nm, may be used as the gate insulating film 510. A single layerstructure or a lamination structure may be used. A 110 nm thick siliconoxynitride film is used in Embodiment 2.

Thereafter, a conductive film having a thickness of 200 to 400 nm isformed and patterned to form gate electrodes 511 to 515. In Embodiment2, the gate electrodes and wirings (hereinafter referred to as gatewirings) electrically connected to the gate electrodes for providingconductive paths are formed of different materials from each other. Morespecifically, the gate wirings are made of a material having a lowerresistivity than the gate electrodes. This is because a materialenabling fine processing is used for the gate electrodes, while the gatewirings are formed of a material that can provide a smaller wiringresistance but is not suitable for fine processing. It is of coursepossible to form the gate electrodes and the gate wirings with the samematerial.

Although the gate electrode can be made of a single-layered conductivefilm, it is preferable to form a lamination film with more than twolayers for the gate electrode if necessary. Any known conductive filmscan be used for the gate electrode. It should be noted, that it ispreferable to use such a material that enables fine processing, and morespecifically, a material that can be patterned with a line width of 2 μmor less.

Typically, it is possible to use a film made of an element selected fromthe croup consisting of tantalum (Ta), titanium (Ti), molybdenum (Mo),tungsten (W), chromium (Cr), and silicon (Si), a film of nitride of theabove element (typically a tantalum nitride film, tungsten nitride film,or titanium nitride film), an alloy film of combination of the aboveelements (typically Mo—W alloy or Mo—Ta alloy), or a silicide film ofthe above element (typically a tungsten silicide film or titaniumsilicide film). Of course, the films may be used as a single layer or alaminate layer.

In Embodiment 2, a laminate film of a tungsten nitride (WN) film havinga thickness of 30 nm and a tungsten (W) film having a thickness of 370nm is used. This may be formed by sputtering. When an inert gas such asXe or Ne is added as a sputtering gas, film peeling due to stress can beprevented.

The gate electrode 511 is formed at this time so as to overlap a portionof the n-type impurity region (b) 505. This overlapping portion laterbecomes an LDD region overlapping the gate electrode (FIG. 10E).

Next, an n-type impurity element (phosphorous is used in Embodiment 2)is added in a self-aligning manner with the gate electrodes 511 to 515as masks, as shown in FIG. 11A. The addition is regulated such thatphosphorous is added to n-type impurity regions (c) 516 to 523 thusformed at a concentration of {fraction (1/10)} to ½ that of the n-typeimpurity region (b) 505 (typically between ¼ and ⅓). Specifically, aconcentration of 1×10¹⁶ to 5×10¹⁸ atoms/cm³ (typically 3×10¹⁷ to 3×10¹⁸atoms/cm³) is preferable.

Resist masks 524 a to 524 c are formed next, with a shape covering thegate electrodes 512 to 515 and the like, as shown in FIG. 11B, and ann-type impurity element (phosphorous is used in Embodiment 2) is added,forming impurity regions (a) 525 to 529 containing phosphorous at highconcentration. Ion doping using phosphine (PH₃) is also performed here,and the phosphorous concentration of these regions is regulated so as tobe set to from 1×10²⁰ to 1×10²¹ atoms/cm³ (typically between 2×10²⁰ and5×10²⁰ atoms/cm³).

A source region or a drain region of the n-channel TFT is formed by thisprocess, and in a switching TFT, a portion of the n-type impurityregions (c) 519 to 521 formed by the process of FIG. 11A is remained.These remaining regions correspond to LDD regions of the switching TFT.

Next, as shown in FIG. 11C, the resist masks 524 a to 524 d are removed,and new resist masks 530 a and 530 b are formed. A p-type impurityelement (boron is used in Embodiment 2) is then added, forming p-typeimpurity regions 531 to 534 containing boron at high concentration.Boron is added here to form the p-type impurity regions 531 to 534 at aconcentration of 3×10²⁰ to 3×10²¹ atoms/cm³ (typically between 5×10²⁰and 1×10²¹ atoms/cm³) by ion doping using diborane (B₂H₆).

Note that phosphorous has already been added to the p-type impurityregions 531 to 534 at a concentration of 1×10²⁰ to 1×10²¹ atoms/cm³, butboron is added here at a concentration of at least 3 times that of thephosphorous. Therefore, the n-type impurity regions already formedcompletely invert to p-type, and function as p-type impurity regions.

Next, after removing the resist masks 530 a and 530 b, the n-type orp-type impurity elements added to the active layer at respectiveconcentrations are activated. Furnace annealing, laser annealing or lampannealing can be used as a means of activation. In Embodiment 2, heattreatment is performed for 4 hours at 550° C. in a nitrogen atmospherein an electric furnace.

At this time, it is critical to eliminate oxygen from the surroundingatmosphere as much as possible. This is because when even only a smallamount of oxygen exists, an exposed surface of the gate electrode isoxidized, which results in an increased resistance and later makes itdifficult to form an ohmic contact with the ate electrode. Accordingly,the oxygen concentration in the surrounding atmosphere for theactivation process is set at 1 ppm or less, preferably at 0.1 ppm orless.

After the activation process is completed, a gate wiring (gate signalline) 535 having a thickness of 300 nm is formed. As a material for thegate wiring 535, a metal film containing aluminum (Al) or copper (Cu) asits main component (occupied 50 to 100% in the composition) can be used.The gate wiring 335 is arranged so as to provide electrical connectionfor the gate electrodes 513 and 514 of the switching TFT (see FIG. 11D).

The above-described structure can allow the wiring resistance of thegate wiring to be significantly reduced, and therefore, an image displayregion (display portion) with a large area can be formed. Morespecifically, the pixel structure in accordance with Embodiment 2 isadvantageous for realizing an EL display device having a display screenwith a diagonal size of 10 inches or larger (or 30 inches or larger.) Afirst interlayer insulating film 537 is formed next, as shown in FIG.12A. A single layer insulating film containing silicon is used as thefirst interlayer insulating film 537, or a lamination film may be used.Further, a film thickness of between 400 nm and 1.5 μm may be used. Alamination structure of an 800 nm thick silicon oxide film on a 200 nmthick silicon oxynitride film is used in Embodiment 2.

In addition, heat treatment is performed for 1 to 12 hours at 300 to450° C. in an atmosphere containing between 3 and 100% hydrogen,performing hydrogenation. This process is one of hydrogen termination ofdangling bonds in the semiconductor film by hydrogen, which is thermallyactivated. Plasma hydrogenation (using hydrogen activated by plasma) mayalso be performed as another means of hydrogenation.

Note that the hydrogenation processing may also be inserted during theformation of the first interlayer insulating film 537. Namely, hydrogenprocessing ma be performed as above after forming the 200 nm thicksilicon oxynitride film, and then the remaining 800 nm thick siliconoxide film may be formed.

Next, a contact hole is formed in the first interlayer insulating film537, and source wirings 538 to 541 and drain wirings 542 to 545 areformed. In this embodiment, this electrode is made of a laminate film ofthree-layer structure in which a titanium film having a thickness of 100nm, an aluminum film containing titanium and having a thickness of 300nm, and a titanium film having a thickness of 150 nm are continuouslyformed by sputtering. Of course, other conductive films may be used.

A first passivation film 547 is formed next with a thickness of 50 to500 nm (typically between 200 and 300 nm) as shown in FIG. 12B. A 300 nmthick silicon oxide nitride film is used as the first passivation film547 in Embodiment 2. This may also be substituted by a silicon nitridefilm. Note that it is effective to perform plasma processing using a gascontaining hydrogen such as H₂ or NH₃ before the formation of thesilicon oxynitride film. Hydrogen activated by this preprocess issupplied to the first interlayer insulating film 537, and the filmquality of the first passivation film 547 is improved by performing heattreatment. At the same time, the hydrogen added to the first interlayerinsulating film 537 diffuses to the lower side, and the active layerscan be hydrogenated effectively.

Next, a second interlayer insulating film 548 made of organic resin isformed. As the organic resin, it is possible to use polyimide,polyamide, acryl, BCB (benzocyclobutene) or the like. Especially, sincethe second interlayer insulating film 548 is primarily used forleveling, acryl excellent in leveling properties is preferable. In thisembodiment, an acrylic film is formed to a thickness sufficient to levela stepped portion formed by TFTs. It is appropriate that the thicknessis made 1 to 5 μm (more preferably, 2 to 4 μm) (FIG. 12B).

Next, a contact hole is formed in the second interlayer insulating film548 and the first passivation film 547 so as to reach the drain wiring543, and a cathode electrode 549 of a light receiving diode(photoelectric converting element) is formed so as to contact the drainwiring 543. Aluminum formed by sputtering is used in this metallic filmin Embodiment 2, but other metals, for example titanium, tantalum,tungsten, and copper can also be used. Further, a lamination film madefrom titanium, aluminum, and titanium may also be used.

Patterning is next performed after depositing an amorphous silicon filmcontaining hydrogen over the entire surface of the substrate, and aphotoelectric converting layer 550 is formed. A transparent conductivefilm is formed on the entire surface of the substrate next. A 200 nmthick ITO film is deposited by sputtering as the transparent conductivefilm in Embodiment 2. The transparent conductive film is patterned,forming an anode electrode 551. (See FIG. 12C.)

A third interlayer insulating film 553 is then formed, as shown in FIG.13A. A level surface can be obtained by using a resin such as polyimide,polyamide, polyimide amide, or acrylic as the third interlayerinsulating film 553. A polyimide film having a thickness of 0.7 μm isformed over the entire surface of the substrate as the third interlayerinsulating film 553 in Embodiment 2.

A contact hole is next formed in the third interlayer insulating film553, the second interlayer insulating film 548, and the firstpassivation film 547 so as to reach the drain wiring 545, and a pixelelectrode 555 is formed. Further, a contact hole for reaching the anodeelectrode 551 is formed in the third interlayer insulating film 553, anda sensor wiring 554 is formed. A 110 nm thick ITO (indium tin oxide)film is formed in Embodiment 2, and then patterning is performed,forming the sensor wiring 554 and the pixel electrode 555 at the sametime. Furthermore, indium oxide mixed with between 2 and 20% of zincoxide (ZnO) may also be used as the transparent conductive film. Thepixel electrode 555 becomes an EL element anode.

A bank 556 is formed next from a resin material. The bank 556 may beformed by patterning an acrylic film or polyimide film having athickness of 1 to 2 μm. The bank 556 is formed having a stripe shapebetween pixels. The bank 556 may be formed along and on the sourcewiring 540, and it may also be formed along and on the ate wiring 535.Note that a material such as a pigment may be mixed into the resinmaterial forming the bank 661, and the bank 661 may be used as ashielding film.

An EL layer 557 and a cathode (MgAg electrode) 558 are formed next insuccession without exposure to the atmosphere by using vacuumevaporation. Note that the film thickness of the EL layer 557 may befrom 80 to 200 nm (typically between 100 and 120 nm), and the thicknessof the cathode 558 may be from 180 to 300 nm (typically between 200 and250 nm). In addition, only one pixel is shown in Embodiment 2, but an ELlayer for emitting red color light, an EL layer for emitting green colorlight, and an EL layer for emitting blue color light are formedsimultaneously.

EL layers 557 are sequentially formed with respect to the pixelcorresponding to the color red, the pixel corresponding to the colorgreen, and the pixel corresponding to the color blue, respectively, bythis process. However, the EL layers 557 have little resistance tosolution, and therefore, the EL layers 557 for the respective colorsmust be formed separately without using photolithography. It is thenpreferable to cover locations other than that of the desired pixels byusing a metal mask, and then form the EL layers 557 selectively only inrequired locations.

In other words, first, a mask for covering everything except for thepixel corresponding to the color red is set, and an EL layer which emitsred color light is selectively formed using the mask. A mask forcovering everything except for the pixel corresponding to the colorgreen is set next, and an EL layer which emits green color light isselectively formed using the mask. Finally, a mask for covering allareas outside of the pixel corresponding to the color blue is set, andan EL layer which emits blue color light is selectively formed using themask. Note that a case of using different masks is stated here, but thesame mask may also be reused. Further, it is preferable to performprocessing without releasing the vacuum until the EL layers of all ofthe pixels have been formed.

Note that the EL layer 557 is a single layer structure composed of onlya light emitting layer in Embodiment 2, but the EL layer 557 may alsohave a hole transport layer, a hole injection layer, an electrontransport layer, and an electron injection layer. Various examples ofthis type of combination have already been reported upon, and any ofthese structures may be used. Known materials can be used as the ELlayer 557. It is preferable to use an organic material as the knownmaterial, considering the EL driver voltage.

The cathode 558 is formed next. An example of using an MgAg electrode asthe cathode of an EL element is shown in Embodiment 2, but it is alsopossible to use other known materials.

An active matrix substrate having the structure shown in FIG. 13B isthus completed. Note that the processes after forming the bank 556 anduntil the formation of the cathode 558 may be performed in succession,without exposure to the atmosphere, using a multi-chamber method (orin-line method) thin film formation apparatus.

Note also that a method of manufacturing a TFT of a sensor portion isexplained in Embodiment 2, but a TFT of a display portion and a drivercircuit TFT may also be formed simultaneously on the substrate.

A buffer TFT 570, which is an n-channel TFT, has a structure inEmbodiment 2 in which hot carrier injection is reduced with as littledrop in operating speed as possible, as shown in FIG. 13B. An activelayer of the buffer TFT 570 contains a source region 580, a drain region581, an LDD region 582, and a channel forming region 583. The LDD region582 overlaps the gate electrode 511 through the gate insulating film510.

The formation of the LDD region on only the drain region side is inconsideration of not causing the operating speed to drop. Further, it isnot necessary to be too concerned with the value of the off current forthe buffer TFT 570, and more importance may be placed on the operatingspeed. It is therefore preferable for the LDD region 582 to completelyoverlap with the gate electrode 511, and to reduce resistive componentsas much as possible. Namely, the so-called offset should be eliminated.

Furthermore, degradation due to hot carrier injection is almost of noconcern for a reset TFT 571 and an EL driving TFT 573, which arep-channel TFTs, and therefore LDD regions do not have to be formed inparticular. It is also possible, of course, to form an LDD regionsimilar to that of an n-channel TFT to take action against hot carriers.

An active layer of a switching TFT 572 in Embodiment 2 contains a sourceregion 590, a drain region 591, LDD regions 592 to 595, channel formingregions 596 and 597, and a separation region 598. The LDD regions 592 to595 are formed so as not to overlap with the gate electrodes 513 and 514through the gate insulating film 510. This type of structure isextremely effective in reducing the off current.

Further, the switching TFT 572 has a double gate structure, and by usingthe double gate structure, this effectively becomes a structure havingtwo TFTs connected in series, and has the advantage of being capable ofreducing the value of the off current. Note that the double gatestructure is used in Embodiment 2, but a single gate structure may alsobe used, and a multiple gate structure possessing more than three gatesmay also be used.

Note also that, in practice, after completing through FIG. 13B, it ispreferable to perform packaging (sealing) using a protective film (suchas a laminate film or an ultraviolet hardened resin film), or a lighttransmitting sealing member, having high airtight properties and littleoutgassing, in order to have no exposure to the atmosphere. The ELelement reliability is increased if the inside of the sealing member isfilled with an inert gas atmosphere and a drying agent (barium oxide,for example) is arranged within the sealing member.

Further, after increasing airtightness by the packaging process, thedevice is completed as a manufactured product by attaching a connector(flexible printed circuit, FPC) for connecting terminals pulled aroundfrom the elements or circuits formed on the substrate with externalsignal terminals. This shipping-ready state is referred to as an ELdisplay (EL module) throughout this specification.

Note that it is possible to implement Embodiment 2 in combination withEmbodiment 1.

Embodiment 3

An example in which light emitted from an EL element is irradiated tothe side of a substrate on which TFTs are formed is explained inEmbodiment 2. Using FIG. 14, an example of irradiating light emittedfrom an EL element to the opposite side of the substrate on which TFTsare formed is explained in Embodiment 3.

Although a p-channel TFT was used for the EL driving TFT in Embodiment2, an n-channel TFT was used for the EL driving TFT in this embodiment.Accordingly, the active later in the EL driving TFT was covered with amask in a process for adding n-type impurity and the active layer in theEL driving TFT was not covered with the mask in the process for addingp-type impurity.

After forming a third interlayer insulating film 653, a contact hole forreaching a drain wiring 645 is formed in the third interlayer insulatingfilm 653, a second interlayer insulating film 648, and a firstpassivation film 647. A pixel electrode 655 is then formed. Further, acontact hole is formed in the third interlayer insulating film 653 inorder to reach an anode electrode 651, and a sensor wiring 654 isformed. A 300 nm thick aluminum alloy film (an aluminum film containing1 wt % of titanium) is formed in Embodiment 3, and patterning is thenperformed, simultaneously forming the sensor wiring 654 and the pixelelectrode 655. Note that although the pixel electrode and the sensorwiring are formed using an aluminum alloy film in Embodiment 3, thepresent invention is not limited to this, and MgAg may also be used.Further, it is possible to use all other materials known to be used asan EL element cathode.

A bank 661 made of a resin material is formed next, as shown in FIG. 14.The bank 661 may be formed by patterning an acrylic film or a polyimidefilm having a thickness of 1 to 2 μm. The bank 661 is formed in a stripeshape between pixels. The bank 661 may be formed on and along a sourcewiring (source signal line) 640, and may be formed on and along a gatewiring (gate signal line) 635. Note that a material such as a pigmentmay be mixed into the resin material forming the bank 661, and the bank661 may be used as a shielding film.

A light emitting layer 656 is formed next. Specifically, an organic ELmaterial which becomes the light emitting layer 656 is dissolved in asolvent such as chloroform, dichloromethane, xylene, toluene, ortetrahydrobenzene, and applied. The solvent is then vaporized byperforming heat treatment, and the organic EL material light emittinglayer is formed.

Note that only one pixel is shown in Embodiment 3, but a light emittinglayer for emitting red color light, a light emitting layer for emittinggreen color light, and a light emitting layer for emitting blue colorlight are formed simultaneously. In Embodiment 3, Cyano-polyphenylenevinylene is formed as the red color light emitting layer, polyphenylenevinylene is formed as the green light emitting layer, andpolyalkylphenylene is formed as the blue light emitting layer, eachhaving a thickness of 50 nm. Further, 1,2-dichloromethane is used as thesolvent, and heat treatment is performed by hotplate at a temperature of80 to 150° C. for between 1 and 5 minutes, vaporizing moisture.

A 20 nm thick hole injection layer 657 is formed next. The holeinjection layer 657 may be formed common for all pixels, and thereforeit may be formed using spin coating or printing. Polythiophene (PEDOT)in aqueous solution is applied in Embodiment 3, and then heat treatmentis performed for 1 to 5 minutes by using a hotplate at a temperaturefrom 100 to 150° C., vaporizing moisture. Polyphenylene vinylene andpolyalkylphenylene do not dissolve in water, and therefore it ispossible in this case to form the hole injection layer 657 withoutdissolution of the light emitting layer 656.

Note that it is also possible to use a low molecular weight organic ELmaterial as the hole injection layer 657. In that case, it may be formedby evaporation.

A two layer structure of a light emitting layer and a hole injectionlayer is taken as the EL layer in Embodiment 3, but in addition, a holetransport layer, an electron injection layer, and an electron transportlayer may also be formed. Various examples of this type of combinationhave already been reported upon, and any of these structures may beused.

An anode 658 is formed, as an opposing electrode, of a 120 nm thicktransparent conductive film after formation of the light emitting layer656 and the hole injection layer 657. A transparent conductive film inwhich 10 to 20 wt % of zinc oxide is added to indium oxide is used inEmbodiment 3. It is preferable to form the anode 658 by evaporation atroom temperature so as not to cause degradation of the light emittinglayer 656 and the hole injection layer 657.

A fourth interlayer insulating film 659 is formed once the anode 658 isformed. A level surface can be obtained by using a resin such aspolyimide, polyamide, polyimide amide, or acrylic as the fourthinterlayer insulating film 659. A 0.7 μm thick polyimide film is formedover the entire surface of the substrate as the fourth interlayerinsulating film 659 in Embodiment 3.

Next, an aluminum alloy film (an aluminum film containing 1 wt % oftitanium) is formed with a thickness of 300 nm on the fourth interlayerinsulating film 659. Patterning is performed, forming a reflecting plate660. It is very important to form the reflecting plate 660 in a positionsuch that light emitted by the EL element is reflected in the reflectingplate 660 and is made incident to a photoelectric converting layer 65 f)of a light receiving diode.

Note that, although the reflecting plate 660 is formed using an aluminumalloy film in Embodiment 3, the present invention is not limited tothis. It is possible to use a known material provided that it is anon-transparent metal. For example, a film of an element selected fromthe group consisting of copper (Cu), silver (Ag), tantalum (Ta),titanium (Ti), molybdenum (Mo), tungsten (W), chromium (Cr), and silicon(Si); or a nitride film of one of these elements (typically a tantalumnitride film, a tungsten nitride film, or a titanium nitride film); oran alloy film of a combination of these elements (typically an Mo—Walloy or an Mo—Ta alloy); or a silicide film of one of these elements(typically a tungsten silicide film or a titanium silicide film) can beused. A single layer structure and a lamination structure may be used,of course.

An active matrix substrate having a structure as shown in FIG. 14 isthus completed. Note that reference numeral 670 denotes a buffer TFT,reference numeral 671 denotes a reset TFT, 672 denotes a switching TFT,and 673 denotes an EL driving TFT.

Note also that the process of manufacturing the TFT of the sensorportion is explained in Embodiment 3, but a TFT of a display portion anda driver circuit TFT may also be formed on the substrate at the sametime.

Further, after completing through FIG. 14, it is preferable in practiceto perform packaging (sealing) using a protective film (such as alaminate film or an ultraviolet hardened resin film), or a lighttransmitting sealing member, having high airtight properties and littleoutgassing, in order to have no exposure to the atmosphere. Thereliability of the EL elements is increased if the inside of the sealingmember is filled with an inert gas atmosphere and a drying agent (bariumoxide, for example) is arranged within the sealing member.

Further, after increasing airtightness by the packaging process, thedevice is completed as a manufactured product by attaching a connector(flexible printed circuit. FPC) for connecting terminals pulled aroundfrom the elements or circuits formed on the substrate with externalsignal terminals. This shipping-ready state is referred to as an ELdisplay (EL module) throughout this specification.

Note that it is possible to implement Embodiment 3 in combination withEmbodiment 1.

Embodiment 4

An EL display of the present invention in which the structure of asensor pixel differs from that of the embodiment mode and those ofEmbodiment 1 to Embodiment 3 is explained in Embodiment 4.

A circuit diagram of the sensor pixel in the EL display of Embodiment 4is shown in FIG. 15. A region that is surrounded by a dotted line is thesensor pixel 704. Contained in the sensor pixel 704 are a source signalline S (any one of the lines between (S1 and Sx)), a power source supplyline V (any one of the lines between (V1 and Vx)), and a gate signalline G (any one of the lines between (G1 and Gy)).

In addition, the sensor pixel 704 has a switching TFT 730, an EL drivingTFT 731, and a sensor EL element 732. A capacitor 733 is provided in thestructure of FIG. 15, but the structure thereof may be formed withoutthe provision of the capacitor 733.

The sensor EL element 732 is composed of an anode, a cathode, and an ELlayer provided therebetween. When the anode is connected to a drainregion of the EL driving TFT 731, the anode is a pixel electrode, andthe cathode is an opposing electrode. On the other hand, when thecathode is connected to the drain region of the EL driving TFT 731, thecathode is the pixel electrode, and the anode is the opposing electrode.

A gate electrode of the switching TFT 730 is connected to the ate signalline G. One of a source region and a drain region of the switching TFT730 is connected to the source signal line S, and the other is connectedto a gate electrode of the EL driving TFT 731.

One of a source region and the drain region of the EL driving TFT 731 isconnected to the power source supply line V, and the other is connectedto the sensor EL element 732. The capacitor 733 is provided so asconnected to the gate electrode of the EL driving TFT 731 and the powersource supply line V.

Further, the sensor pixel 704 has a reset TFT 734, a buffer TFT 735, anda sensor TFT 736.

It is preferable that one of the reset TFT 734 and the buffer TFT 735 ofthe sensor pixel 704 be an n-channel TFT and that the remaining TFT be ap-channel TFT. Furthermore, it is preferable that the polarity of thebuffer TFT 735 and the sensor TFT 736 be the same.

A gate electrode of the reset TFT 734 is connected to a reset signalline RL. A source region of the reset TFT 734 is connected to a sensorpower source line VB and a drain region of the buffer TFT 735. Thesensor power source line VB is constantly held at a fixed electricpotential (standard electric potential). Furthermore, a drain region ofthe reset TFT 734 is connected to a drain region of the sensor TFT 736and a gate electrode of the buffer TFT 735.

A source region of the buffer TFT 735 is connected to a sensor outputwiring FL. The sensor output wiring FL is further connected to aconstant-current power source 737 and a fixed current constantly flowstherein. Further, a drain region of the buffer TFT 735 is connected tothe sensor power source line VB which is constantly maintained at afixed standard electric potential. The buffer TFT 735 functions as asource follower.

A source region of the sensor TFT 736 is maintained at a predeterminedelectric potential. A gate electrode of the sensor TFT 736 is thenconnected to a sensor TFT power source line SVB and is always maintainedat a fixed electric potential. The electric potential difference V_(GS)between the gate electrode and the source region of the sensor TFT ismaintained such that the sensor TFT is always maintained in the OFFstate. Note that the source region and the gate electrode of the sensorTFT 736 may also have an electrically connected, structure. In thiscase, the electric potential difference V_(GS) between the gateelectrode and the source region of the sensor TFT is 0 V, and thereforethe sensor TFT will always be in the OFF state.

Drive of the sensor pixel 704 is explained next.

First, the reset TFT 734 is placed in the ON state in accordance with areset signal inputted by the reset signal line RL. The standard electricpotential of the sensor power source line VB is therefore applied to thegate electrode of the buffer TFT 735. The source region of the bufferTFT 735 is then connected to constant-current power source through thesensor output wiring FL, and the electric potential difference V_(GS)between the source region and the gate electrode of the buffer TFT 735is always fixed. The source region of the buffer TFT 735 is thereforemaintained at an electric potential in which V_(GS) is subtracted fromthe standard electric potential. Note that a period during which thereset TFT 734 is in the ON state is referred to as a reset periodthroughout this specification.

Next, the electric potential of the reset signal inputted to the resetsignal line RL is changed and the reset TFT 734 is placed in the OFFstate. The standard electric potential of the sensor power source lineVB is therefore not applied to the gate electrode of the buffer TFT 735.Note that a period during which the reset TFT 734 is in the OFF state isreferred to as a sample period throughout this specification.

Note also that it is possible to drive an EL display having the sensorpixel shown in Embodiment 4 by a digital method and by an analog method.For a case of digital drive, it is preferable that the sample period belonger than the address period Ta.

When light from the sensor EL element 732 is irradiated to the sensorTFT 736, the off current flows in a channel forming region of the sensorTFT 736. It is very important that the sensor TFT 736 be a bottom gateTFT. The electric potential of the gate electrode of the buffer TFT 735therefore changes in the sample period, and the size of the electricpotential change varies in accordance with the amount of off currentflowing in the channel forming region of the sensor TFT 736.

The off current flowing in the channel forming region of the sensor TFT736 is proportional to the strength of light irradiated to the sensorTFT 736 because the electric potential difference V_(GS) between thegate electrode and the source region of the sensor TFT 736 is fixed. Inother words, comparing when the luminance of the sensor EL element 732is high and when it is low, when the luminance is high, a large offcurrent flows in accordance with the channel forming region of thesensor TFT 736. Therefore, compared with when the luminance of thesensor EL element 732 is low, the changes in the electric potential ofthe gate electrode of the buffer TFT 735 become larger when theluminance is high.

The electric potential difference V_(GS) between the source region andthe gate electrode of the buffer TFT 735 is always fixed. Therefore,when the electric potential of the gate electrode of the buffer TFT 735changes, the electric potential of the source region of the buffer TFT735 also changes in accordance with the gate electrode change. Thesource region of the buffer TFT 735 is maintained at an electricpotential in which V_(GS) is subtracted from the electric potential ofthe gate electrode of the buffer TFT 735.

The electric potential of the source region of the buffer TFT 735 isapplied to the sensor output wiring FL, and is inputted to a correctioncircuit or a video signal correction circuit as a sensor output signal.

A cross sectional diagram of an EL display of Embodiment 4 having thesensor pixel 704 is shown in FIG. 16. In FIG. 16, reference numeral 811denotes a substrate and 812 denotes an insulating film which becomes abase (hereafter referred to as a base film). A transparent substrate,typically a glass substrate, a quartz substrate, a glass ceramicsubstrate, or a crystalline glass substrate can be used as the substrate811. Note that a material which can withstand the maximum processingtemperature attained during the manufacturing processes must be used.

Further, the base film 812 is particularly effective for a case of usinga substrate containing a mobile ion and a substrate having conductivityneed not be formed for a quartz substrate. An insulating film containingsilicon may be used as the base film 812. Note that an “insulating filmcontaining silicon” indicates an insulating film containing apredetermined ratio of oxygen and nitrogen with respect to silicon, suchas a silicon oxide film, a silicon nitride film, or a silicon oxynitridefilm (denoted by SiOxNv, where x and v are arbitrary integers).

Reference numeral 735 denotes the buffer TFT, 734 denotes the reset TFT,736 denotes the sensor TFT, 730 denotes the switching TFT, and 731denotes the EL driving TFT. The buffer TFT 735, the switching TFT 730,and the sensor TFT 736 are each formed by an n-channel TFT. Further, thereset TFT 734 and the EL driving TFT 731 are both formed by a p-channelTFT.

When the direction of EL light emitted is toward the substrate side, itis preferable that the switching TFT and the EL driving TFT have theabove structure. However, the present invention is not limited to thisstructure. The switching TFT and the EL driving TFT may be n-channelTFTs and may be p-channel TFTs. Furthermore, the reset TFT 734 and thebuffer TFT 735 may have mutually differing polarities, and may ben-channel TFTs and may be p-channel TFTs. The sensor TFT 736 may also bean n-channel TFT or a p-channel TFT, provided that it has the samepolarity as the buffer TFT 735.

The switching TFT 730 has an active layer containing a source region813, a drain region 814. LDD regions 815 a to 815 d, a separation region816, and channel forming regions 817 a and 817 b; a gate insulating film818; gate electrodes 819 a and 819 b; a first interlayer insulating film820; a source wiring (source signal line) 821; a drain wiring 822; andchannel forming region protective films 863 and 864. Note that the gateinsulating film 818 and the first interlayer insulating film 820 may becommon among all TFTs on the substrate, or may differ depending upon thecircuit or the element.

Furthermore, the switching TFT 730 shown in FIG. 16 is electricallyconnected to the gate electrodes 817 a and 817 b, becoming a double gatestructure. A multi-gate structure (a structure containing an activelayer having two or more channel forming regions connected in series)such as a triple gate structure, may of course also be used, in additionto the double gate structure.

The multi-gate structure is extremely effective in reducing the offcurrent, and provided that the off current of the switching TFT issufficiently lowered, a capacitor connected to the gate electrode of theEL driving TFT 731 can have its capacitance reduced to the minimumnecessary. In other words, the surface area of the capacitor can be madesmaller, and therefore using the multi-gate structure is also effectivein expanding the effective light emitting surface area of the ELelements.

In addition, the LDD regions 815 a to 815 d are formed so as not tooverlap the gate electrodes 819 a and 819 b through the gate insulatingfilm 818 in the switching TFT 730. This type of structure is extremelyeffective in reducing the off current. Furthermore, the length (width)of the LDD regions 815 a to 815 d may be set from 0.5 to 3.5 μm,typically between 2.0 and 2.5 μm.

Note that forming an offset region (a region which is a semiconductorlayer having the same composition as the channel forming region and towhich the gate voltage is not applied) between the channel formingregion and the LDD region is additionally preferable in a point that theoff current is lowered. Further, when using a multi-gate structurehaving two or more gate electrodes, the separation region 816 (a regionto which the same impurity element, at the same concentration, as thatadded to the source region or the drain region, is added) providedbetween the channel forming regions is effective in reducing the offcurrent.

Next, the EL driving TFT 731 is formed having an active layer containinga source region 826, a drain region 827, and a channel forming region829; the gate insulating film 818; a gate electrode 830, the firstinterlayer insulating film 820; a channel forming region 865; a sourcewiring 831; and a drain wiring 832.

Further, the drain region 814 of the switching TFT 730 is connected tothe gate 830 of the EL driving TFT 731. Although not shown in thefigure, specifically the oate electrode 830 of the EL driving TFT 731 iselectrically connected to the drain region 814 of the switching TFT 730through the drain wiring (also referred to as a connection wiring) 822.Note that the gate electrode 830 has a single gate structure, but amulti-oate structure may also be used. Further, the source wiring 831 ofthe EL driving TFT 731 is connected to a power source supply line (notshown in the figure).

The EL driving TFT 731 is an element for controlling the amount ofelectric current injected to the EL element, and a relatively largeamount of current flows in the EL driving TFT 731. It is thereforepreferable to design the channel width W to be larger than the channelwidth of the switching TFT 730. Further, it is preferable to design thechannel length L such that an excess of electric current does not flowin the EL driving TFT 731. It is preferable to have from 0.5 to 2 μA(more preferably between 1 and 1.5 μA) per pixel.

In addition, by making the film thickness of the active layer(particularly the channel forming region) of the EL driving TFT 731thicker (preferably from 50 to 100 nm, even better between 60 and 80nm), degradation of the TFT may be suppressed. Conversely, in the caseof the switching TFT 730 it is also effective to make the film thicknessof the active layer (particularly the channel forming region) thinner(preferably from 20 to 50 nm, and more preferably between 25 and 40 nm)from the standpoint of making the off current smaller.

The buffer TFT 735, the reset TFT 734, and the sensor TFT 736 havesource wirings 845, 846, and 885, respectively. Further, the similarlyhave drain wirings 847, 848, and 887; gate electrodes 843, 839, and 883;source regions 840, 835, and 880; channel forming regions 842, 838, and882 drain regions 841, 836, and 881; the gate insulating film 818; thefirst interlayer insulating film 820; the channel forming regionprotective films 861, 862, and 867; and LDD regions 844 a, 844 b, 884 a,and 884 b, respectively.

Note that in Embodiment 4, the LDD regions 844 a, 844 b, 884 a, and 884b are formed in the buffer TFT 735 and the sensor TFT 736, but astructure having no LDD regions may also be used. Further, a structurehaving one LDD region in each source region side or drain region sidemay also be used.

There is almost no concern with degradation of the reset TFT 734, whichis a p-channel TFT, due to hot carrier injection, and therefore no LDDregion need be formed in particular. It is possible to take measuresagainst hot carrier injection by forming an LDD region similar to thatof the buffer TFT 735 and the sensor TFT 736, which is an n-channel TFT,of course.

Note that the channel forming region protective films 861 to 865 aremasks for forming the channel forming regions 842, 838, 817 a, 817 b,829, and 882. It is necessary for light to pass through the channelforming region protective films 861 to 865.

Next, reference numeral 849 denotes a first passivation film, and itsfilm thickness may be set from 10 nm to 1 μm (preferably between 200 and500 nm). An insulating film containing silicon (in particular, it ispreferable to use a silicon oxynitride film or a silicon nitride film)can be used as the passivation film material. The passivation film 847possesses a role of protecting the TFTs from alkaline metals andmoisture. Alkaline metals such as sodium are contained in an EL layer854 formed on the final TFT (in particular, the EL driving TFT). Inother words, the first passivation film 849 works as a protecting layerso that these alkaline metals (mobile ions) do not penetrate into theTFT side.

Further, reference numeral 851 denotes a second interlayer insulatingfilm, which has a function as a leveling film for performing leveling ofa step due to the TFTs. An organic resin film is preferable as thesecond interlayer insulating film 851, and one such as polyimide,polyamide, acrylics or BCB (benzocyclobutene) may be used. These organicresin films have the advantages of easily forming a good, level surface,and having a low specific dielectric constant. The EL layer is extremelysensitive to unevenness, and therefore it is preferable to nearly absorbthe TFT step by the second interlayer insulating film 851. In addition,it is preferable to form the low specific dielectric constant materialthickly in order to reduce the parasitic capacitance formed between thegate signal wiring and the data signal wiring, and the cathode of the ELelement. The thickness, therefore, is preferably from 0.5 to 5 μm (morepreferably between 1.5 and 2.5 μm).

Further, reference numeral 852 denotes a pixel electrode (an anode of anEL element) made of a transparent conductive film. After forming acontact hole (opening) in the second interlayer insulating film 851 andin the first passivation film 849, the pixel electrode 852 is formed soas to be connected to the drain wiring 832 of the EL driving TFT 731.Further, reference numeral 860 denotes a sensor wiring made from atransparent conductive film, and after opening a contact hole (opening)in the second interlayer insulating film 851 and the first passivationfilm 849, the sensor wiring 860 is formed so as to connect to the sourcewiring 885 of the sensor TFT 736 in the formed opening, at the same timeas the pixel electrode 852. Note that if the pixel electrode 852 and thedrain region 827 are formed so as to not be directly connected as inFIG. 16, then alkaline metals of the EL layer can be prevented fromentering the active layer via the pixel electrode.

A third interlayer insulating film 853 is formed on the pixel electrode852 and the sensor wiring 860 from a silicon oxide film, a siliconnitride oxide film, or an organic resin film, with a thickness from 0.3to 1 μm. An opening is formed in the third interlayer insulating film853 over the pixel electrode 852 by etching, and the edge of the openingis etched so as to become a tapered shape. The taper angle may be setfrom 10 to 60°, (preferably between 30 and 50°).

An EL layer 854 is formed on the third interlayer insulating film 853. Asingle layer structure or a lamination structure can be used for the ELlayer 854, but the lamination structure has good light emittingefficiency. In general, a hole injection layer, a hole transport layer,a light emitting layer, and an electron transport layer are formed inorder on the electrode, but a structure having a hole transport layer, alight emitting layer, and an electron transport layer, or a structurehaving a hole injection layer, a hole transport layer, a light emittinglayer, an electron transport layer, and an electron injection layer mayalso be used. Any known structure may be used by the present invention,and doping of a fluorescing pigment or the like into the EL layer mayalso be performed.

The structure of FIG. 16 is an example of a case of forming three typesof EL elements corresponding to R, G, and B. Note that although only onepixel is shown in FIG. 16, pixels having an identical structure areformed corresponding to red, green and blue colors, respectively, andthat color display can thus be performed. It is possible to implementthe present invention without depending upon the method of colordisplay.

A cathode 855 of the EL element is formed on the EL layer 854 as anopposing electrode. A material containing a low work coefficientmaterial such as magnesium (Mg), lithium (Li), or calcium (Ca), is usedas the cathode 855. Preferably, an electrode made from MgAg (a materialmade from Mg and Ag at a mixture of Mg:Ag=10:1) is used. In addition, aMgAgAl electrode, an LiAl electrode, and an LiFAl electrode can be givenas other examples.

It is preferable to form the cathode 855 in succession, without exposureto the atmosphere, after forming the EL layer 854. This is because theinterface state between the cathode 855 and the EL layer 854 greatlyinfluences the light emitting efficiency of the EL element. Note that,throughout this specification, a light emitting element formed by apixel electrode (anode), an EL layer, and a cathode is referred to as anEL element. Note also that FIG. 16 shows a cross sectional diagram ofthe sensor pixel, and therefore a location in which the pixel electrode852, the EL layer 854, and the opposing electrode 855 are surrounded bya dotted line is the sensor EL element 732.

The lamination body composed of the EL layer 854 and the cathode 855must be formed separately for each pixel, but the EL layer 854 isextremely weak with respect to moisture, and consequently a normalphotolithography technique cannot be used. It is therefore preferable touse a physical mask material such as a metal mask, and to selectivelyform the layers by a gas phase method such as vacuum evaporation,sputtering, or plasma CVD.

Note that it is also possible to use a method such as ink jet printingor screen printing as the method of selectively forming the EL layer854. However, the cathode cannot currently be formed in succession withthese methods, and therefore it is preferable to use the other methodsstated above.

Further, a protecting electrode may also be formed on the opposingelectrode 855. The protecting electrode protects the cathode 855 fromexternal moisture and the like, and at the same time is an electrode forconnecting the cathodes 855 of each pixel. It is preferable to use a lowresistance material containing aluminum (Al), copper (Cu), or silver(Ag) as the protecting electrode. The protecting electrode can also beexpected to have a heat radiating effect which relieves the amount ofheat generated by the EL layer. Further, it is effective to form theprotecting electrode in succession, without exposure to the atmosphere,after forming the EL layer 854 and the cathode 855.

Note that it goes without saying that all of the TFTs shown in FIG. 16may have a polysilicon film as their active layer.

The present invention is not limited to the structure of the EL displayof FIG. 16, and the structure of FIG. 16 is only one preferredembodiment for implementing the present invention.

Embodiment 5

An example of an external view of an EL display of the present inventionis explained in Embodiment 5.

FIG. 17A is a top view of an EL display of the present invention. InFIG. 17A, reference numeral 4010 denotes a substrate, reference numeral4011 denotes a display portion, reference numeral 4012 denotes a sourcesignal line driver circuit, and reference numeral 4013 denotes a gatesignal line driver circuit. The driver circuits are connected to anexternal device via wirings 4014 to 4016, which lead to an FPC 4017.

Further, a sensor portion 4019 is connected to the display portion 4011in by a wiring 4020, and is connected to a correction circuit or a videosignal correction circuit provided outside the substrate by a wiring4018 leading to the FPC 4017. Note that although the correction circuit,or the video signal correction circuit, is provided outside thesubstrate in Embodiment 5, the present invention is not limited to such,and the correction circuit, or the video signal correction circuit, maybe provided on the substrate.

A cover member 6000, a sealing member (also referred to as a housingmaterial) 7000, and a sealant (a second sealing member) 7001 areprovided at this point so as to surround at least the display portion4011 and the sensor portion 4019, and preferably to surround the drivercircuits 4012 and 4013, the sensor portion 4019, and the display portion4011.

Further, FIG. 17B shows in cross section the structure of the EL displayof Embodiment 5, and a driver circuit TFT (note that a CMOS circuitcombining an n-channel TFT and a p-channel TFT is shown here) 4022 and aTFT of a display pixel (note that only an EL driving TFT for controllingthe electric current to an EL element is shown here) 4023 are formed onthe substrate 4010 and a base film 4021. Note that a TFT of a sensorpixel is not shown in the figure here. These TFTs have a known structure(a top gate structure or a bottom gate structure).

After the driver circuit TFT 4022 and the EL driver circuit TFT 4023 arecompleted using a known method of manufacture, a pixel electrode 4027made from a transparent conductive film electrically connected to adrain of the EL driving TFT 4023 is formed on an interlayer insulatingfilm (leveling film) 4023 made from a resin material. A compound ofindium oxide and tin oxide (referred to as ITO) or a compound of indiumoxide and zinc oxide can be used as the transparent conductive film. Aninsulating film 4028 is formed once the pixel electrode is formed, andan opening is formed on the pixel electrode 4027.

An EL layer 4029 is formed next. A lamination structure obtained byfreely combining known EL materials (a hole injection layer, a holetransport layer, a light emitting layer, an electron transport layer,and an electron injection layer), or a single layer structure, may beused for the EL layer 4029. A known technique may be used to form such astructure. Further, there are low molecular weight materials and highmolecular weight materials (polymer materials) among the EL materialsform forming the EL layer. An evaporation method is used when a lowmolecular weight material is used, while it is possible to use a simplemethod such as printing, or inkjet method when a high molecular weightmaterial is used.

The EL layer is formed by evaporation using a shadow mask in Embodiment5. Color display becomes possible by forming light emitting layers (ared color light emitting layer, a green color light emitting layer, anda blue color light emitting layer) capable of emitting light atdifferent wavelength for each pixel using the shadow mask. In addition,a method of combining a color changing layer (CCM) and a color filter,and a method of combining a white color light emitting layer and a colorfilter are available, and both may be used. A single color lightemitting EL display can also be made, of course.

After forming the EL layer 4029, a cathode 4030 is formed on top. It ispreferable to remove as much moisture and oxygen as possible from theinterface between the cathode 4030 and the EL layer 4029. A method inwhich the EL layer 4029 and the cathode 4030 are formed in successionwithin a vacuum, or a method in which the EL layer 4029 is formed in aninert atmosphere and the cathode 4030 is then formed without exposure tothe atmospheric air is therefore necessary. The above film formation canbe performed by using a multi-chamber method (cluster chamber method)film formation apparatus.

Note that a lamination structure of a LiF (lithium fluoride) film and anAl (aluminum) film is used as the cathode 4030 in Embodiment 5.Specifically, a 1 nm thick LiF (lithium fluoride) film is formed byevaporation on the EL layer 4029, and a 300 nm thick aluminum film isformed on the LiF film. An MgAg electrode, which is a known cathodematerial, may of course be used instead. The cathode 4030 is thenconnected to the wiring 4016 in a region denoted by reference numeral4031. The wiring 4016 is an power source supply line for applying apredetermined voltage to the cathode 4030, and is connected to the FPC4017 through a conductive paste material 4032.

The cathode 4030 and the wiring 4016 are electrically connected in theregion shown by reference numeral 4031, and therefore it is necessary toform contact holes in the interlayer insulating film 4026 and in theinsulating film 4028. These contact holes may be formed during etchingof the interlayer insulating film 4026 (when the pixel electrode contacthole is formed) and during etching of the insulating film 4028 (whenforming the opening before forming the EL layer). Further, the contactholes may also be formed by etching in one shot through the interlayerinsulating film 4026 when etching the insulating film 4028. A contacthole having a good shape can be formed in this case provided that theinterlayer insulating film 4026 and the insulating film 4028 are formedfrom the same resin material.

A passivation film 6003, a filler material 6004 and the cover member6000 are formed covering the surface of the EL element thus formed.

In addition, the sealing member 7000 is formed in a space defined by thecover member 6000 and the substrate 4010 so as to surround the ELelement containing the pixel electrode 4027, the EL layer 4029, and thecathode 4030. The sealant (the second sealing member) 7001 is formed onthe outside of the sealing member 7000.

Further, a filler 6004 is provided so as to cover the EL element. Thefiller 6004 also functions as an adhesive for bonding a cover member6000. As the filler 6004, PVC (polyvinyl chloride), epoxy resin,silicone resin. PVB (polyvinyl butyral) or EVA (ethylene-vinyl acetate)may be used. Preferably, a desiccant is provided in the filler 6004 tomaintain a moisture absorbing effect.

The filler 6004 may also contain a spacer. The spacer may be particlesof BaO or the like so that the spacer itself has a moisture absorbingeffect.

If a spacer is provided, the passivation film 6003 can reduce the spacerpressure. A resin film or the like may also be provided independently ofthe passivation film to reduce the spacer pressure.

As the cover member 6000, a glass sheet, an aluminum sheet, a stainlesssteel sheet, an FRP (fiberglass-reinforced plastic) sheet, a PVF(polyvinyl fluoride) film, a Mylar film, a polyester film, an acrylicfilm, or the like may be used. If PVB or EVA is used as the filler 6004,it is preferable to use a sheet having a structure in which an aluminumfoil having a thickness of several tens of urn is sandwiched between PVFor Mylar films.

Some setting of the direction of luminescence from the EL element (thedirection in which light is emitted) necessitates making the covermember 6000 transparent.

Also the wiring 4016 is electrically connected to the FPC (flexibleprinted circuit) 4017 by being passed through a gap between the sealingmember 7000, the sealant 7001, and the substrate 4010. While theelectrical connection of the wiring 4016 has been described, otherwirings 4014, 4015, and 4018 are also connected electrically to the FPC4017 by being passed under the sealing member 7000 and the sealant 7001.

In Embodiment 5, after the filler 6004 has been provided, the covermember 6000 is bonded and the sealing member 7000 is attached so as tocover the side surfaces (exposed surfaces) of the filler 6004. However,the filler 6004 may be provided after attachment of the cover member6000 and the sealing member 7000. In such a case, a filler injectionhole is formed which communicates with a cavity formed by the substrate4010, the cover member 6000 and the sealing member 7000. The cavity isevacuated to produce a vacuum (at 10-2 Torr or lower), the injectionhole is immersed in the filler in a bath, and the air pressure outsidethe cavity is increased relative to the air pressure in the cavity,thereby filling the cavity with the filler.

Embodiment 6

An example of an external view of an EL display of the presentinvention, differing from that of Embodiment 5, is explained inEmbodiment 6 with reference to FIGS. 18A and 18B. Reference numeralswhich are the same as those of FIGS. 17A and 17B denote the samecomponents, and therefore an explanation of these components is omitted.

FIG. 18A is a top view of the EL display of Embodiment 6, and FIG. 18Bis a cross-sectional view taken along the line A-A′ in FIG. 18A.

Internal portions of the EL device below a passivation film 6003 whichcovers a surface of the EL element are formed in the same manner asEmbodiment 5.

The filler 6004 also functions as an adhesive for bonding a cover member6000. As the filler 6004, PVC (polyvinyl chloride), epoxy resin,silicone resin, PB (polyvinyl butyral) or EVA (ethylene-vinyl acetate)may be used. Preferably, a desiccant is provided in the filler 6004 tomaintain a moisture absorbing effect.

The filler 6004 may also contain a spacer. The spacer may be particlesof BaO or the like so that the spacer itself has a moisture absorbingeffect.

If a spacer is provided, the passivation film 6003 can reduce the spacerpressure. A resin film or the like may also be provided independently ofthe passivation film to reduce the spacer pressure.

As the cover member 6000, a glass sheet, an aluminum sheet, a stainlesssteel sheet, an FRP (fiberglass-reinforced plastic) sheet, a PVF(polyvinyl fluoride) film, a Mylar film, a polyester film, an acrylicfilm, or the like may be used. If PVB or EVA is used as the filler 6004,it is preferable to use a sheet having a structure in which an aluminumfoil having a thickness of several tens of μm is sandwiched between PVFor Mylar films.

Some setting of the direction of luminescence from the EL element (thedirection in which light is emitted) necessitates making the covermember 6000 transparent.

Next, the cover member 6000 is bonded by using the filler 6004.Thereafter, a frame member 6001 is attached so as to cover side surfaces(exposed surfaces) of the filler 6004. The frame member 6001 is bondedby a sealing member 6002 (functioning as an adhesive). Preferably, aphoto-setting resin is used as the sealing member 6002. However, athermosetting resin may be used if the heat resistance of the EL layeris high enough to allow use of such a resin. It is desirable that thesealing member 6002 has such properties as to inhibit permeation ofmoisture and oxygen as effectively as possible. A desiccant may be mixedin the sealing member 6002.

Also wiring 4016 is electrically connected to a flexible printed circuit(FPC) 4017 by being passed through a gap between the sealing member 6002and the substrate 4010. While the electrical connection of the wiring4016 has been described, other wirings 4014, 4015 and 4018 are alsoconnected electrically to the FPC 4017 by being passed under the sealingmember 6002.

In Embodiment 6, after the filler 6004 has been provided, the covermember 6000 is bonded and the frame member 6001 is attached so as tocover the side surfaces (exposed surfaces) of the filler 6004, however,the filler 6004 may be provided after attachment of the cover member6000, the sealing member 6002, and the frame member 6001. In such acase, a filler injection hole is formed which communicates with a cavityformed by the substrate 4010, the cover member 6000, the sealing member6002, and the frame member 6001. The cavity is evacuated to produce avacuum (at 10⁻² Torr or lower), the injection hole is immersed in thefiller in a bath, and the air pressure outside the cavity is increasedrelative to the air pressure in the cavity, thereby filling the cavitywith the filler.

Embodiment 7

A more detailed cross sectional structure of a display portion in an ELdisplay is shown in FIG. 19, a top structure thereof is shown in FIG.20A, and a circuit diagram thereof is shown in FIG. 20B. Common symbolsare used in FIG. 19 and FIGS. 20A and 20B, and therefore they may bemutually referenced.

In FIG. 19, a switching TFT 3502 formed on a substrate 3501 is ann-channel TFT formed by a known method. A double gate structure is usedin Embodiment 7, but there are no large differences in the structure andthe manufacturing process, and therefore an explanation is omitted. Notethat by using the double gate structure, in effect this becomes astructure in which two TFTs are connected in series, which has theadvantage of being capable of reducing the value of the off current.Note also that although the double gate structure is used in Embodiment7, a single gate structure and a triple gate structure may also be used,and a multi-ate structure possessing more than three gates may also beused. Furthermore, a p-channel TFT formed by using a known method mayalso be used.

An n-channel TFT formed by a known method is used as an EL driving TFT3503. A drain wiring 35 of the switching TFT 3502 is electricallyconnected to a gate electrode 37 of the EL driving TFT 3503 by a wiring36. Further, a wiring denoted by reference numeral 38 is a gate wiringfor electrically connecting gate electrodes 39 a and 39 b of theswitching TFT 3502.

The EL driving TFT 3503 is an element for controlling the amount ofelectric current flowing in a display EL element, and therefore muchcurrent flows therein. Therefore the EL driving TFT 3503 is an elementhaving a high risk of deterioration due to heat and due to hot carriers.An LDD region overlapping the gate electrode through a gate insulatingfilm may therefore be provided on the drain side of the EL driving TFT3503, through which deterioration due to heat and due to hot carriers isprevented.

The EL driving TFT 3503 having a single gate structure is shown in thefigures in Embodiment 7, but a multi-gate structure in which a pluralityof TFTs are connected in series may also be used. In addition, astructure in which a plurality of TFTs are connected in parallel andsubstantially dividing a channel forming region into a plurality ofchannel forming regions, so that heat can be released wraith highefficiency may also be used. This type of structure is effective as ameasure against deterioration due to heat.

Furthermore, as shown in FIG. 20A, the wiring 36 which includes the gateelectrode 37 of the EL driving TFT 3503 overlaps with a drain wiring 40of the EL driving TFT 3503 through the insulating film in a regiondenoted by, reference numeral 3504. A storage capacitance is formed inthe region shown by reference numeral 3504 at this point. The storagecapacitance 3504 is formed from a semiconductor film 3520 which iselectrically connected to an power source supply line 3506, aninsulating film (not shown in the figures) on the same layer as the gateinsulating film, and the wiring 36. Further, it is also possible to usea capacitor formed from the wiring 36, the same layer (not shown in thefigures) as that of a first interlayer insulating film, and the powersource supply line 3506 as a storage capacitance. The storagecapacitance 3504 functions as a capacitor for storing a voltage appliedto the gate electrode 37 of the EL driving TFT 3503. Note that the drainof the EL driving TFT 3503 is connected to the power source supply line(power source supply line) 3506, and a fixed voltage is always applied.

A first passivation film 41 is formed on the switching TFT 3502 and theEL driving TFT 3503, and a leveling film 42 is formed on top of thatfrom an insulating resin film. It is extremely important to level thestep due to the TFTs using the leveling film 42. An EL layer formedlater is extremely thin, so there are cases in which defective lightemissions occur because of the presence of the step. Therefore, to formthe EL layer on as level a surface as possible, it is preferable toperform leveling before forming a pixel electrode.

Furthermore, reference numeral 43 denotes a pixel electrode (display ELelement cathode) made from a conductive film with high reflectivity, andthis is electrically connected to a drain region of the EL driving TFT3503. It is preferable to use for the pixel electrode 43 a lowresistance conductive film, such as an aluminum alloy film, a copperalloy film, and a silver alloy film, or a laminate of such films. Ofcourse, a lamination structure with another conductive film may also beused.

In addition, a light emitting layer 45 is formed in the middle of agroove (corresponding to a pixel) formed by banks 44 a and 44 b, whichare formed of insulating films (preferably resins). In FIG. 20A, thebanks are partially omitted in order to clarify the position of thestorage capacitance 3504, showing only the banks 44 a and 44 b. However,the banks are provided between pixels so as to partially cover the powersource supply line 3506 and the source wiring 34. Note that only twopixels are shown in the figures here, but light emitting layers may beformed so as to correspond to the colors R (red), G (green), and B(blue), respectively. A T conjugate polymer type material is used as anorganic EL material. PPV(Polyparaphenylene vinylene) type, PVK(polyvinyl carbazole) type, and polyfluorene type can be given astypical polymer type materials.

Note that there are several kinds of PPV type organic EL materials, andmaterials disclosed in Shenk, H., Becker, H., Gelsen, O., Kluge, E.,Kreuder. W., and Spreitzer, H., “Polymers for Light Emitting Diodes”,Euro Display Proceedings. 1999, pp. 33-7, and in Japanese PatentApplication Laid-open No. Hei 10-92576, for example, may be used.

As specific light emitting layers, cyano-polyphenylene vin ylene may beused as a red light emitting layer, polyphenylene vinylene may be usedas a green light emitting layer, and polyphenylene vinylene orpolyalkylphenylene may be used as a blue light emitting layer. The filmthicknesses may be between 30 and 150 nm (preferably between 40 and 100nm).

However, the above is an example of the organic EL materials which canbe used as light emitting layers, and it is not necessary to be limitedto these materials. An EL layer (a layer for emitting light and formoving carriers for light emission) may be formed by freely combininglight emitting layers, an electric charge transport layer, and anelectric charge injection layer.

For example, Embodiment 7 shows an example of using a polymer typematerial as a light emitting layer, but a low molecular weight organicEL material may also be used. Further, it is possible to use inorganicmaterials such as silicon carbide, as an electric charge transport layeror an electric charge injection layer. Known materials can be used forthese organic EL materials and inorganic materials.

A lamination structure EL layer, in which a hole injection layer 46 madefrom PEDOT (polythiophene) or PAni (polyaniline) is formed on the lightemitting layer 45, is used in Embodiment 7. An anode 47 is then formedon the hole injection layer 46 from a transparent conductive film. Thelight generated by the light emitting layer 45 is radiated toward theupper surface (toward the top of the TFT) in Embodiment 7., andtherefore the anode must be light-transmissive. An indium oxide and tinoxide compound, or an indium oxide and zinc oxide compound can be usedfor the transparent conductive film. However, because it is formed afterforming the low heat resistance light emitting layer and hole injectionlayer, it is preferable to use a material which can be deposited at aslow a temperature as possible.

An EL element 3505 is completed at the point where the anode 47 isformed. Note that what is called the EL element 3505 here is a capacitorformed of the pixel electrode (cathode) 43, the light emitting layer 45,the hole injection layer 46, and the anode 47. The pixel electrode 43 isnearly equal in area to the pixel, and consequently the entire pixelfunctions as an EL element. Therefore, the light emission efficiency isextremely high, and a bright image display becomes possible.

In addition, a second passivation film 48 is then formed on the anode 47in Embodiment 7. It is preferable to use a silicon nitride film or asilicon oxynitride film as the second passivation film 48. The purposeof this is the isolation of the display EL element from the outside, andthis for preventing degradation due to oxidation of the organic ELmaterial, as well as for controlling degas from the organic EL material.The reliability of the EL display can thus be raised.

The EL display panel of the present invention has a display portionformed of pixels structured as in FIG. 19, and has a switching TFT witha sufficiently low off current value, and an EL driving TFT which isstrong against hot carrier injection. An EL display which has highreliability and which is capable of displaying a good image cantherefore be obtained.

Note that it is possible to implement the constitution of Embodiment 4by freely combining it with the constitutions of the embodiment mode andEmbodiment 1.

Embodiment 8

A structure in which the structure of the display EL element 3505 in thepixel portion shown in Embodiment 7 is inverted is explained inEmbodiment 8. FIG. 21 is used in the explanation. Note that the onlypoints of difference between the structure of FIG. 21 and that of FIG.19 is the display EL element and the EL driving TFT 3503, and thereforean explanation of other portions is omitted.

An EL driving TFT 3503 in FIG. 21 is a p-channel TFT manufactured byusing a known method. Refer to the manufacturing process of Embodiment 2in forming the p-channel TFT.

A transparent conductive film is used as a pixel electrode (anode) 50 inEmbodiment 5. Specifically, a conductive film made from a compound ofindium oxide and zinc oxide is used. Of course, a conductive film madefrom a compound of indium oxide and tin oxide may also be used.

After then forming banks 51 a and 51 b from insulating films, a lightemitting layer 52 is formed from polyvinyl carbazole by solutioncoating. An electron injection layer 53 is formed on the light emittinglayer from potassium acetylacetonate (expressed as acacK), and a cathode54 is formed from an aluminum alloy. In this case the cathode 54 alsofunctions as a passivation film. A display EL element 3701 is thusformed.

The light generated by the light emitting layer 52 is radiated towardthe substrate on which the TFT is formed in Embodiment 8, as shown bythe arrows.

Note that it is possible to implement the constitution of Embodiment 5by freely combining it with the constitution of any of Embodiments 1 to3.

Embodiment 9

In Embodiment 9, an example of a case of a pixel having a structurewhich differs from that of the circuit diagram shown in FIG. 20B isshown in FIGS. 22A to 22C. Note that, in Embodiment 9, reference numeral3801 denotes a source signal line which is a portion of a source wiringof a switching TFT 3802, reference numeral 3803 denotes a gate signalline which is a portion of a gate wiring of a switching TFT 3802,reference numeral 3804 denotes an EL driving TFT, 3805 denotes acapacitor, 3806 and 3808 are power source supply lines, and referencenumeral 3807 denotes a display EL element.

FIG. 22A is an example of a case in which the power source supply line3806 is common between two pixels. The case of FIG. 22A is characterizedin that two pixels are formed so as to be symmetric with respect to thepower source supply line 3806. In this case the number of power sourcesupply lines can be reduced, and a display portion can have even higherdefinition.

Further, FIG. 22B is an example of a case of forming the power sourcesupply line 3808 in parallel with the gate signal line 3803. Note thatFIG. 22B has a structure in which the power source supply line 3808 andthe gate signal line 3803 are formed so as not to overlap, but providedthat the two are formed on differing layers, they can be formed so as tooverlap through an insulating film. In this case the surface areaoccupied by the power source supply line 3808 and the gate signal line3803 can be shared, and therefore the display portion can have evenhigher definition.

In addition. FIG. 22C has a structure characterized in that the powersource supply line 3808 is formed in parallel to the gate signal lines3803 as in the structure shown in FIG. 22B, and in addition, two pixelsare formed so as to be symmetric with respect to the power source supplyline 3808. Furthermore, it is also effective to form the power sourcesupply line 3808 so as to overlap with one of the gate signal lines3803. In this case the number of power source supply lines can bereduced, and the display portion can have even higher definition.

Note that it is possible to implement the constitution of Embodiment 9by freely combining with the constitution of any of the embodiment modeand Embodiments 1 to 6 and 8. Furthermore, it is effective to use the ELdisplay having the pixel structure of Embodiment 9 as a display deviceof electronic equipment in Embodiment 11.

Embodiment 10

A structure in which a storage capacitance for maintaining a voltageapplied to a gate electrode of an EL driving TFT is omitted is explainedin Embodiment 10. For a case in which the EL driving TFT is an n-channelTFT and has an LDD region formed so as to overlap with the gateelectrode through a gate insulating film, a parasitic capacitancegenerally referred to as a gate capacitor is formed in the overlappingregion. This parasitic capacitor is actively used as a substitute for astorage capacitance, which characterizes Embodiment 10.

The capacitance of the parasitic capacitor changes in accordance withthe surface area in which the gate electrode and the LDD region overlap,and is determined by, the length of the LDD region included in theoverlapping region.

Further, it is also possible to similarly omit the storage capacitancein the structures of FIGS. 22A, 22B, and 22C shown in Embodiment 9.

Note that it is possible to implement the constitution of Embodiment 10by freely combining it with the constitution of any of Embodiments 1 to9. Further, it is effective to use the EL display having the pixelstructure of Embodiment 10 as a display device of electronic equipmentin Embodiment 11.

Embodiment 11

The present invention is not limited to a structure in which a lightreceiving diode in a sensor pixel detects only the luminance of lightemitted from a sensor EL element. The light receiving diode of thesensor pixel may also detect the luminance of light from outside of anEL display (external light) in addition to the luminance of the light ofthe sensor EL element, and correction of the luminance of the EL elementmay be performed by adjusting to the external luminance. For instance,correction is made such that the luminance of the EL element is loweredwhen the luminance of the external light is high, and when the luminanceof the external light is low, on the other hand, the EL elementincreases its luminance.

According to the above structure, a clear image can be displayedirrespective of the luminance of the surroundings.

Embodiment 12

An EL display of the present invention in which the structure of asensor pixel differs from that shown in the embodiment mode, andEmbodiments 1 to 4 is described.

A circuit diagram of a sensor pixel of Embodiment 12 is the same as thatof the EL display shown in the embodiment mode, and therefore FIG. 3 isreferenced. The structure of a light receiving diode in Embodiment 12differs from that of the embodiment mode. A cross sectional diagram of asensor pixel of Embodiment 12 is shown in FIG. 25 in order to explainthe structure of the light receiving diode of Embodiment 12.

Reference numeral 935 denotes a buffer TFT, reference numeral 934denotes a reset TFT, 936 denotes a light receiving diode, 930 denotes aswitching TFT, 931 denotes an EL driving TFT, and reference numeral 932denotes a sensor EL element.

The light receiving diode 936 has an anode 980, a cathode 981, a channelforming region 983, a buffer region 984, an anode wiring 985, and acathode wiring 986 within an active layer.

The anode 980 and the cathode 981 of Embodiment 12 are formed by dopinga p-type impurity or an n-type impurity to an essentially intrinsicsemiconductor body. Note that the polarity of the impurity added to theanode 980 and to the cathode 981 is the same. Further, the impurityadded to the anode 980 and to the cathode 981 is added to the bufferregion 984 at a concentration which is lower than that in the anode 980and in the cathode 981.

It is preferable that the polarity of the impurity added to a sourceregion and a drain region of the buffer TFT 935 be the same as that ofthe impurity added to the anode 980 and to the cathode 981 of the lightreceiving diode 936. The cathode 981 of the light receiving diode 936 iselectrically connected to a drain region of the reset TFT 934 and to agate electrode of the buffer TFT 935. The anode 980 of the lightreceiving diode 936 is maintained at a fixed electric potential.

Electric current flows in the light receiving diode 936 when the lightreceiving diode 936 is irradiated with light from the sensor EL element932. The electric potential of the gate electrode of the buffer TFT 935,which is fixed during the reset period, therefore changes in the sampleperiod, and the amount of change of the electric potential changes inaccordance with the amount of the electric current flowing in the lightreceiving diode 936.

The electric current flowing in the light receiving diode 936 isproportional to the intensity of the light irradiating the lightreceiving diode 936. Namely, comparing when the luminance of the lightof the sensor EL element 932 is high and when it is low, when theluminance is high a large off current flows in the light receiving diode936. The changes in the electric potential of the gate electrode of thebuffer TFT 935 therefore is larger when the luminance of the light ofthe sensor EL element 932 is high compared to when the luminance thereofis low.

The electric potential difference V_(GS) between the source region andthe gate electrode of the buffer TFT 935 is always fixed, and thereforethe source region of the buffer TFT 935 is maintained at an electricpotential in which V_(GS) is subtracted from the electric potential ofthe gate electrode of the buffer TFT 935. When the electric potential ofthe gate electrode of the buffer TFT 935 changes, the electric potentialof the source region of the buffer TFT 935 also changes inaccompaniment.

The electric potential of the source region of the buffer TFT 935 isgiven to a sensor output wiring FL, and is inputted to a correctioncircuit or a video signal correction circuit as a sensor output signal.

Without newly adding new manufacturing steps for the light receivingdiode, the light receiving diode can be formed simultaneously with theother TFTs and the number of steps for manufacturing the EL display canbe reduced with Embodiment 12.

Embodiment 13

An EL display device formed by implementing the present invention hassuperior visibility in bright locations in comparison to a liquidcrystal display device because it is a self-emissive type device, andmoreover its field of vision is wide. Accordingly, it can be used as adisplay portion for various electronic devices. For example, it isappropriate to use the EL display device of the present invention as adisplay portion of an EL display (a display incorporating the EL displaydevice in its casing) having a diagonal equal to 30 inches or greater(typically equal to 40 inches or greater) for appreciation of TVbroadcasts by large screen.

Note that all displays exhibiting (displaying) information such as apersonal computer display, a TV broadcast reception display, or anadvertisement display are included as the EL display device. Further,the EL display device of the present invention can be used as a displayportion of the other various electronic devices.

The following can be given as examples of such electronic devices: avideo camera; a digital camera a goggle type display (head mounteddisplay); a car navigation system; an audio reproducing device (such asa car audio system, an audio compo system); a notebook personalcomputer; a game equipment; a portable information terminal (such as amobile computer, a mobile telephone, a mobile game equipment or anelectronic book); and an image playback device provided with a recordingmedium (specifically, a device which performs playback of a recordingmedium and is provided with a display which can display those images,such as a digital versatile disk (DVD)). In particular, because portableinformation terminals are often viewed from a diagonal direction, thewideness of the field of vision is regarded as very important. Thus, itis preferable that the EL display device is employed. Examples of theseelectronic devices are shown in FIGS. 23A to 24B.

FIG. 23A is an EL display, containing a casing 2001, a support stand2002, a display portion 2003 and a sensor portion 2004. The presentinvention can be used in the display portion 2003 and a sensor portion2004. Since the EL display is a self-emissive type device without theneed of a backlight, its display portion can be made thinner than aliquid crystal display device.

FIG. 23B is a video camera, containing a main body 2101, a displayportion 2102, an audio input portion 2103, operation switches 2104, abattery 2105, an image receiving portion 2106 and a sensor portion 2107.The EL display device of the present invention can be used in thedisplay portion 2102 and a sensor portion 2107.

FIG. 23C is a portion of a head fitting type EL display (right side),containing a main body 2201, a signal cable 2202, a head fixing band2203, a display portion 2204, an optical system 2205, an EL displaydevice 2206 and a sensor portion 2207. The present invention can be usedin the EL display device 2206 and a sensor portion 2207.

FIG. 23D is an image playback device (specifically, a DVD playbackdevice) provided with a recording medium, containing a main body 2301, arecording medium (such as a DVD) 2302, operation switches 2303, adisplay portion (a) 2304, a display portion (b) 2305 and a sensorportion 2306. The display portion (a) 2304 is mainly used for displayingimage information, and the image portion (b) 2305 is mainly used fordisplaying character information, and the EL display device of thepresent invention can be used in the image portion (a) 2304, in theimage portion (b) 2305 and in the sensor portion 2306. Note thatdomestic game equipment is included as the image playback deviceprovided with a recording medium.

FIG. 23E is a goggle type display (head mounted display), containing amain body 2401, a display portion 2402, an arm portion 2403 and a sensorportion 2404. The present invention can be used in the display portion2402 and the arm portion 2403. In the FIG. 23E, while a sensor portion2404 is provided in an arm portion 2403, the present invention is notlimited to the structure. The sensor portion 2404 can be provided in arow with the display portion 2402.

FIG. 23F is a personal computer, containing a main body 2501, a casing2502, a display portion 2503, a keyboard 2504 and a sensor porting 2505.The EL display device of the present invention can be used in thedisplay portion 2503 and a sensor portion 2505.

Note that in the future if the emission luminance of EL materialsbecomes higher, the projection of light including output images can beenlarged by lenses or the like. Then it will become possible to use theEL display device of the present invention in a front type or a reartype projector.

The above electronic devices are becoming more often used to displayinformation provided through an electronic transmission circuit such asthe Internet or CATV (cable television), and in particular,opportunities for displaying animation information are increasing. Theresponse speed of EL materials is extremely high, and therefore the ELdisplay device is favorable for performing animation display.

The emitting portion of the EL display device consumes power, andtherefore it is preferable to display information so as to have theemitting portion become as small as possible. Therefore, when using theEL display device in a display portion which mainly displays characterinformation, such as a portable information terminal, in particular, aportable telephone and an audio reproducing device, it is preferable todrive it by setting non-emitting portions as background and formingcharacter information in emitting portions.

FIG. 24A is a portable telephone, containing a main body 2601, an audiooutput portion 2602, an audio input portion 2603, a display portion2604, operation switches 2605, an antenna 2606 and a sensor 2607. The ELdisplay device of the present invention can be used in the displayportion 2604 and the sensor 2607. Note that by displaying whitecharacters in a black background in the display portion 2604, the powerconsumption of the portable telephone can be reduced.

FIG. 24B is an audio reproducing device, specifically a car audiosystem, containing a main body 2701, a display portion 2702, andoperation switches 2703, 2704 and a sensor portion 2705. The EL displaydevice of the present invention can be used in the display portion 2702and a sensor portion 2705. Furthermore, an audio reproducing device fora car is shown in this embodiment, but it may also be used for a mobiletype and a domestic type of audio reproducing device. Note that bydisplaying white characters in a black background in the display portion2704, the power consumption can be reduced. This is particularlyeffective in a mobile type audio reproducing device.

The range of applications of the present invention is thus extremelywide, and it is possible to apply the present invention to electronicdevices in all fields. Furthermore, any constitution of the EL displaydevice shown in Embodiments 1 to 12 may be employed in the electronicdevices of this embodiment.

According to the present invention, even if the speed of deteriorationof an EL layer is influenced by factors such as the structure of adevice driving an EL display, the properties of an EL materialstructuring the EL layer, an electrode material, the conditions in themanufacturing process, and a method of driving the EL display, an ELdisplay capable of displaying a clear image having a desired color canbe provided.

Further, by forming a display EL element and a sensor EL element at thesame conditions and at the same time, the speed of deterioration of theEL layers of the display EL element and of the sensor EL element can bemade the same. Therefore, the luminance of the sensor EL element which alight receiving diode detects becomes very close to the luminance of thedisplay EL element, and changes in the luminance of the display ELelement can be more accurately detected, making it possible to correctto obtain desired luminance.

Furthermore, when a sensor portion is formed on a substrate at the sametime as a display portion, a process of manufacturing an EL display hasonly an additional step of forming the light receiving diode, comparedto a case of not forming the sensor portion. It is therefore notnecessary to have a considerable increase in the number of manufacturingsteps, and it is possible to suppress the number of manufacturingprocesses.

Note that by using a portion of the display portion as the sensorportion, the space for forming the sensor portion can be curtailedcompared to a case of not including the sensor portion in the displayportion, and therefore the size of the EL display can be reduced.

1-38. (Cancelled)
 39. A digital camera having a display device, thedisplay device comprising: a substrate; a plurality of display pixelsformed over the substrate; a sensor pixel formed adjacent to theplurality of the display pixels and over the substrate; and a correctioncircuit formed over the substrate, wherein the sensor pixel has atransistor, an EL element and a light receiving diode, wherein thecorrection circuit is connected to the transistor.
 40. A digital cameraaccording to claim 39, wherein a luminance of each of plurality of thedisplay pixels is controlled by the amount of a current flowing in thelight receiving diode.
 41. A digital camera according to claim 39,wherein the EL element comprises an anode, a cathode and an EL layertherebetween.
 42. A digital camera according to claim 41, wherein the ELlayer comprises at least one organic material selected from the groupconsisting of Alq₃, TPD, PPV, PVK and polycarbonate.
 43. A digitalcamera having a display device, the display device comprising: asubstrate; a plurality of display pixels formed over the substrate; asensor pixel formed adjacent to the plurality of the display pixels; anda correction circuit formed over the substrate, wherein the sensor pixelhas a transistor, an EL element and a light receiving diode, wherein thecorrection circuit is connected to the transistor.
 44. A digital cameraaccording to claim 43, wherein a luminance of each of plurality of thedisplay pixels is controlled by the amount of a current flowing in thelight receiving diode.
 45. A digital camera according to claim 43,wherein the EL element comprises an anode, a cathode and an EL layertherebetween.
 46. A digital camera according to claim 45, wherein the ELlayer comprises at least one organic material selected from the groupconsisting of Alq₃, TPD, PPV, PVK and polycarbonate.
 47. A digitalcamera having a display device, the display device comprising: asubstrate; a plurality of display pixels formed over the substrate; asensor pixel formed adjacent to the plurality of the display pixels andover the substrate; and a correction circuit formed over the substrate,wherein the sensor pixel has a transistor, an EL element and aphotosensor, wherein the correction circuit is connected to thetransistor.
 48. A digital camera according to claim 47, wherein aluminance of each of plurality of the display pixels is controlled bythe amount of a current flowing in the photosensor.
 49. A digital cameraaccording to claim 47, wherein the EL element comprises an anode, acathode and an EL layer therebetween.
 50. A digital camera according toclaim 49, wherein the EL layer comprises at least one organic materialselected from the group consisting of Alq₃, TPD, PPV, PVK andpolycarbonate.
 51. A digital camera having a display device, the displaydevice comprising: a substrate; a plurality of display pixels formedover the substrate; a sensor pixel formed adjacent to the plurality ofthe display pixels and over the substrate; and a correction circuitformed over the substrate, wherein the sensor pixel has a transistor, anEL element and a light receiving diode, wherein the correction circuitis connected to a gate of the transistor.
 52. A digital camera accordingto claim 51, wherein a luminance of each of plurality of the displaypixels is controlled by the amount of a current flowing in the lightreceiving diode.
 53. A digital camera according to claim 51, wherein theEL element comprises an anode, a cathode and an EL layer therebetween.54. A digital camera according to claim 53, wherein the EL layercomprises at least one organic material selected from the groupconsisting of Alq₃, TPD, PPV, PVK and polycarbonate.
 55. A digitalcamera having a display device, the display device comprising: asubstrate; a plurality of display pixels formed over the substrate; asensor pixel formed adjacent to the plurality of the display pixels andover the substrate; and a correction circuit formed adjacent to theplurality of the display pixels, wherein the sensor pixel has atransistor, an EL element and a light receiving diode, wherein thecorrection circuit is connected to the transistor.
 56. A digital cameraaccording to claim 55, wherein a luminance of each of plurality of thedisplay pixels is controlled by the amount of a current flowing in thelight receiving diode.
 57. A digital camera according to claim 55,wherein the EL element comprises an anode, a cathode and an EL layertherebetween.
 58. A digital camera according to claim 57, wherein the ELlayer comprises at least one organic material selected from the groupconsisting of Alq₃, TPD, PPV, PVK and polycarbonate.
 59. A personalinformation terminal having a display device, the display devicecomprising: a substrate; a plurality of display pixels formed over thesubstrate; a sensor pixel formed adjacent to the plurality of thedisplay pixels and over the substrate; and a correction circuit formedover the substrate, wherein the sensor pixel has a transistor, an ELelement and a light receiving diode, wherein the correction circuit isconnected to the transistor.
 60. A personal information terminalaccording to claim 59, wherein a luminance of each of plurality of thedisplay pixels is controlled by the amount of a current flowing in thelight receiving diode.
 61. A personal information terminal according toclaim 59, wherein the EL element comprises an anode, a cathode and an ELlayer therebetween.
 62. A personal information terminal according toclaim 61, wherein the EL layer comprises at least one organic materialselected from the group consisting of Alq₃, TPD, PPV, PVK andpolycarbonate.
 63. A personal information terminal having a displaydevice, the display device comprising: a substrate; a plurality ofdisplay pixels formed over the substrate; a sensor pixel formed adjacentto the plurality of the display pixels; and a correction circuit formedover the substrate, wherein the sensor pixel has a transistor, an ELelement and a light receiving diode, wherein the correction circuit isconnected to the transistor.
 64. A personal information terminalaccording to claim 63, wherein a luminance of each of plurality of thedisplay pixels is controlled by the amount of a current flowing in thelight receiving diode.
 65. A personal information terminal according toclaim 63, wherein the EL element comprises an anode, a cathode and an ELlayer therebetween.
 66. A personal information terminal according toclaim 65, wherein the EL layer comprises at least one organic materialselected from the group consisting of Alq₃, TPD, PPV, PVK andpolycarbonate.
 67. A personal information terminal having a displaydevice, the display device comprising: a substrate; a plurality ofdisplay pixels formed over the substrate; a sensor pixel formed adjacentto the plurality of the display pixels and over the substrate; and acorrection circuit formed over the substrate, wherein the sensor pixelhas a transistor, an EL element and a photosensor, wherein thecorrection circuit is connected to the transistor.
 68. A personalinformation terminal according to claim 67, wherein a luminance of eachof plurality of the display pixels is controlled by the amount of acurrent flowing in the photosensor.
 69. A personal information terminalaccording to claim 67, wherein the EL element comprises an anode, acathode and an EL layer therebetween.
 70. A personal informationterminal according to claim 69, wherein the EL layer comprises at leastone organic material selected from the group consisting of Alq₃, TPD,PPV, PVK and polycarbonate.
 71. A personal information terminal having adisplay device, the display device comprising: a substrate; a pluralityof display pixels formed over the substrate; a sensor pixel formedadjacent to the plurality of the display pixels and over the substrate;and a correction circuit formed over the substrate, wherein the sensorpixel has a transistor, an EL element and a light receiving diode,wherein the correction circuit is connected to a gate of the transistor.72. A personal information terminal according to claim 71, wherein aluminance of each of plurality of the display pixels is controlled bythe amount of a current flowing in the light receiving diode.
 73. Apersonal information terminal according to claim 71, wherein the ELelement comprises an anode, a cathode and an EL layer betweentherebetween.
 74. A personal information terminal according to claim 73,wherein the EL layer comprises at least one organic material selectedfrom the group consisting of Alq₃, TPD, PPV, PVK and polycarbonate. 75.A personal information terminal having a display device, the displaydevice comprising: a substrate; a plurality of display pixels formedover the substrate; a sensor pixel formed adjacent to the plurality ofthe display pixels and over the substrate; and a correction circuitformed adjacent to the plurality of the display pixels, wherein thesensor pixel has a transistor, an EL element and a light receivingdiode, wherein the correction circuit is connected to the transistor.76. A personal information terminal according to claim 75, wherein aluminance of each of plurality of the display pixels is controlled bythe amount of a current flowing in the light receiving diode.
 77. Apersonal information terminal according to claim 75, wherein the ELelement comprises an anode, a cathode and an EL layer therebetween. 78.A personal information terminal according to claim 77, wherein the ELlayer comprises at least one organic material selected from the groupconsisting of Alq₃, TPD, PPV, PVK and polycarbonate.